King Pin to Gooseneck Adapter: 5 Top Picks Compared

Towing a gooseneck trailer with a fifth-wheel hitch can be a puzzle. A king pin to gooseneck adapter is the simple solution, converting your trailer’s king pin to fit a gooseneck ball in your truck bed. This guide compares five top adapters, helping you find the perfect match for your setup and budget.

Whether you need a heavy-duty option for a work trailer or a cushioned model for a smoother RV ride, we’ve got you covered. Read on to discover the key features and differences between these popular choices.

FlexHitch 30K Lbs GTW Adapter – Cost-Saving Conversion

The FlexHitch adapter is designed to save you money by converting your existing gooseneck trailer’s 4-inch round tube to a standard 2-inch king pin. This means you can tow your gooseneck trailer using your truck’s fifth-wheel hitch without installing a separate gooseneck system. The bolt-on installation is straightforward, requiring no welding or cutting, so you can get set up with basic hand tools.

Built from heavy-duty carbon steel, this adapter handles up to 30,000 lbs GTW and 4,500 lbs tongue weight, making it suitable for substantial loads. A key benefit is the dual-towing flexibility: you can keep your fifth-wheel hitch in place and switch between towing a fifth-wheel and a gooseneck trailer as needed. The reinforced rib design adds extra strength where it counts.

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• Cost-Saving Compatibility Solution – No need to install a full gooseneck hitch system hitch for your pickup This adapter converts your gooseneck trailer’s 4" round tube to a 2" standard kingpin interface, letting your existing 5th-wheel hitch tow the trailer seamlessly
• Easy Bolt-On Installation – No welding, cutting, or professional modifications required! Replace the original gooseneck ball coupler on your trailer’s 4" round tube with basic hand tools in 15 minutes. Perfect for truck owners who prefer hassle-free at-home upgrades
• Heavy-Duty Load Capacity for Reliable Towing – Built with heavy duty carbon steel, this adapter boasts a 30,000 lbs GTW (Gross Trailer Weight) and 4,500 lbs tongue weight rating. Ideal for hauling heavy cargo, farm equipment, and construction materials without wobbling or failure
• Dual-Towing Flexibility Without Hitch Removal – Keep your pickup’s 5th-wheel hitch intact while gaining the ability to tow gooseneck trailers. Switch between 5th-wheel RVs and gooseneck flatbeds in minutes—no repeated uninstallation/installation, perfect for multi-purpose towing needs.
• Precision Fit for 4" Round Tube Trailers – Engineered with a tight 0.5mm gap tolerance to fit all standard 4" round tube gooseneck trailer frames. Eliminates towing noise and instability at high speeds, ensuring a secure, smooth ride whether on highways or rough off-road terrain

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Misakomo Fifth Wheel to Gooseneck Adapter – Precision Forged

The Misakomo adapter is engineered from robust forged steel with precise one-piece machining, ensuring maximum strength and durability for your towing needs. It features a dependable 2-inch king pin and a 2-5/16 inch gooseneck ball with a 3/5-inch bolster, designed for heavy-duty towing up to 30,000 lbs. The 8-inch diameter middle disc is specially crafted to better handle the dynamic forces during turns and maneuvers.

Installation is hassle-free, allowing you to quickly convert your fifth-wheel trailer for gooseneck towing. This adapter is built to last, with a black finish that resists corrosion. It’s a straightforward solution for those who need a reliable, high-capacity adapter without extra frills. The one-piece construction minimizes potential failure points, giving you confidence on the road.

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• Built to Last – The kingpin to gooseneck ball adapter is engineered with robust forged steel and precise one-piece machining for maximum strength and durability. This ensures a uniform distribution of force and a high resistance to breakage. It’s topped off with a protective coating for outstanding rust resistance, making it ideal for withstanding both severe weather and the test of time.
• Heavy-Duty Towing Capacity – This fifth wheel hitch adapter features a dependable 2-inch kingpin and a 2-5/16 inch gooseneck ball with a 3/5" bolster, engineered for maximum towing performance. It is capable of handling up to 30,000 lbs of gross trailer weight, perfect for securely transporting large fifth-wheel and gooseneck trailers.
• Precision Designed – Specially crafted for trailer-fifth wheels, the 5th wheel to gooseneck adapter's 8" diameter middle disc is optimized to better handle the dynamic forces during towing and reduce potential wobble, ensuring a stable and safe journey.
• Installation Made Simple – The 2085295 Gooseneck Ball Adapter offers a hassle-free installation, allowing for quick and secure attachment of your gooseneck or fifth wheel trailer to your truck, without the need for welding or extensive modifications. Simply adjust the main post of your gooseneck trailer as needed to ensure a level tow.
• Usage Guidelines – Ensure the fifth wheel is securely locked in an upright position to avoid tilting or unnecessary stress on the adapter. For trailers with an offset gooseneck, stabilize the fifth wheel plate to prevent articulation. Be cautious with pick-up type fifth wheels that swivel 360°, as they may not be compatible with this adapter.
• Verify Product Dimensions – Before making a purchase, please confirm the dimensions of this gooseneck ball adapter. Not all adapters are identical or share the same measurements. It is essential to verify that this adapter is compatible with your trailer and towing setup BEFORE PURCHASING to ensure a proper fit and avoid any compatibility issues.

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PSAUTO Cushioned Trailer Hitch Adapter – Smooth Ride

The PSAUTO cushioned gooseneck adapter converts your fifth-wheel trailer’s king pin into a gooseneck connection in minutes, but its standout feature is the cushioned design. This provides a smoother, more comfortable towing experience by absorbing road shocks and reducing jarring movements. It’s ideal for RVs and campers where passenger comfort matters.

With an adjustable height range from 12 to 16 inches, you can fine-tune the setup for level towing, which improves stability and weight distribution. The adapter is easy to install without drilling or welding, fitting directly into your trailer’s king pin box. While specific capacity details are not listed, the cushioned design prioritizes ride quality over raw capacity, making it a great choice for lighter trailers.

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• The cushioned gooseneck adapter converts your 5th wheel into a gooseneck within minutes.

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Weonefit C5G1216 Adjustable Cushioned Adapter – Versatile Support

The Weonefit C5G1216 adapter converts your trailer’s king pin to connect to a gooseneck hitch, with a fully cushioned design that provides 360-degree support plus up-and-down movement. This ensures exceptional stability and safety under various road conditions, reducing stress on your trailer and truck. It’s a great replacement for camper, RV, or trailer king pin boxes.

With a towing capacity of 20,000 lbs and a pin weight capacity of 4,000 lbs, it’s suited for medium-duty trailers. The height is adjustable from 12 to 16 inches, allowing you to achieve a level towing position. Installation is easy with no drilling or welding required, and it comes with safety chains for added security. The cushioned feature makes it a top pick for those who prioritize ride quality.

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• ★【Versatile Compatibility】- C5G1216 Coupler Adapter is used to convert a trailer's kingpin to connect to a Gooseneck Hitch. Replacement for Camper/RV/Trailer's Kingpin Box- 12"-16". The sliding collar with set screws allows it to be adjusted to any height between 12" and 16". Not recommended for trucks with beds shorter than 6 feet or cushioned style king pin boxes.
• ★【Product Specification】- Towing capacity: 20,000 lb. Pin weight capacity: 4,000 lb. Gooseneck Adapter: 12"-16". Cushioned 360˚, plus up and down. No drilling or welding required. With Safty Chain. Installation instructions not included.
• ★【Adjustable Height Settings】- Our gooseneck adapter features a fully cushioned design that provides 360-degree support, ensuring exceptional stability and safety under various conditions. This fully adjustable model allows users to easily modify the height, ranging from 12 inches to 16 inches, measured from the top of the gooseneck ball to the kingpin plate. This flexible height adjustment capability ensures that the adapter can perfectly fit different vehicle and trailer configurations.
• ★【Easy Installation & Enhanced Safety】- Weonefit 5th wheel adapter to gooseneck is engineered for a straightforward bolt-on installation, allowing you to easily attach it to your existing 5th wheel setup without the need for specialized tools or extensive mechanical knowledge. This user-friendly design ensures that you can quickly get back on the road, saving you time and effort. This adapter includes locking pins to secure the connection between your truck and trailer.
• ★【After-Sales Service】- Long life-span matters, that is why our Gooseneck Adapter is made of high quality material, strong and corrosion resistant to ensure it can work for a long time. We are committed to provide the best products and services for every customer. If you are not sure whether our products are compatible with your model or the product does not meet your expectations, please contact us, we will try our best till your satisfaction.

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TOWGUARD Gooseneck to 5th Wheel Kit – Complete Solution

The TOWGUARD adapter kit is a complete solution for converting a gooseneck trailer with a 4-inch square tube to a fifth-wheel king pin. It includes the inner tube, making installation more straightforward than basic adapters. The adjustable multi-hole design provides up to 6 inches of vertical adjustment, helping you achieve a level towing setup for better weight distribution and handling.

Built for demanding work, this rigid steel adapter has a 30,000-lb capacity, suitable for flatbeds, heavy utility trailers, and equipment hauling. The reinforced gusset base with a lock pin ensures secure attachment and added strength at the connection point. This kit is ideal for those who need a heavy-duty, adjustable solution for their square-tube gooseneck trailer.

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• COMPLETE ADAPTER KIT FOR 4" SQUARE TUBE APPLICATIONS This kit includes the inner tube, creating a more complete gooseneck-to-fifth-wheel conversion solution. Designed for 4-inch square tube trailer applications and a standard 2" fifth wheel king pin hitch connection.
• HEIGHT ADJUSTABLE FOR LEVEL TOWING The adjustable multi-hole design provides up to 6 inches of vertical adjustment to help create a better level towing setup. Useful for matching different truck heights, trailer stances, and hauling conditions where towing balance matters.
• 30K LBS HEAVY-DUTY CAPACITY Built for demanding work with a 30,000-lb capacity, this rigid steel adapter kit is made for flatbeds, heavy utility trailers, equipment hauling, livestock trailers, agricultural towing, and other serious trailer applications.
• REINFORCED GUSSET BASE WITH LOCK PIN SECURITY The lower section features a reinforced gusset base to strengthen the king pin connection area, while the included lock pin adds a more complete retaining solution for users who want a more secure and ready-to-install setup.
• INCLUDES 2 FIFTH WHEEL HITCH LUBE PLATES Comes with 2 fifth wheel hitch lube plates to help reduce friction, lower grease mess, and minimize wear on the hitch contact surface. A practical addition for cleaner maintenance and repeated towing use.
• Professional Towing Guidance & After-Sales Support TOWGUARD provides towing setup recommendations, fitment assistance, and after-sales technical support. If you have questions regarding compatibility, towing configuration, or product coverage, please contact us at towguardsc@163.com. Our team is committed to delivering reliable support and product confidence.

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Buyer’s Guide: What to Consider

Choosing the right king pin to gooseneck adapter depends on your trailer type, weight, and towing preferences. Here are five key factors to consider.

• Capacity: Match the adapter's GTW and tongue weight ratings to your trailer's gross weight. Overloading can be dangerous.
• Tube Type: Adapters fit either round or square tubes. Measure your trailer's tube to ensure compatibility before buying.
• Height Adjustment: Adjustable height helps achieve a level towing position, improving stability and reducing wear on your hitch.
• Cushioned vs. Rigid: Cushioned adapters absorb road shocks for a smoother ride, while rigid ones offer maximum strength for heavy loads.
• Installation: Most adapters bolt on without welding. Check if the kit includes all necessary hardware for a hassle-free setup.

Conclusion

Selecting the best king pin to gooseneck adapter comes down to your specific trailer and towing needs. For a cost-effective conversion of a round-tube gooseneck, the FlexHitch is a solid choice. If you need a robust, forged steel adapter, the Misakomo delivers durability. For a smoother ride in an RV, the PSAUTO or Weonefit cushioned models are excellent. The TOWGUARD kit is ideal for square-tube trailers requiring height adjustment.

Consider your trailer’s tube type, weight, and whether you prioritize comfort or raw capacity. Any of these five adapters will help you tow with confidence.