5 Best King Pin Plate for Semi Trailer

When you’re hauling heavy loads, the king pin plate on your semi trailer is the critical link between tractor and trailer. A weak or worn king pin can lead to dangerous disconnects and costly downtime.

This guide reviews five top king pin plates and accessories, from heavy-duty forged steel options to anti-theft locks, helping you choose the right fit for your fifth wheel setup.

Buyers Products KP20050 Forged King Pin – Heavy-Duty 0.50-Inch Plate

The Buyers Products KP20050 is built for the toughest jobs. With a 2-inch SAE king pin and a 0.50-inch bolster plate thickness, it provides exceptional strength for heavy-duty semi trailers. The forged construction maintains a hardness of 302-363 BHN, ensuring it withstands repeated coupling and road stress without deforming.

This weldable king pin integrates seamlessly into your existing bolster plate, making installation straightforward for a qualified welder. Buyers Products designs their components with the same care they’d use for their own equipment, so you can trust the KP20050 to deliver reliable performance mile after mile. It’s a solid choice if you need maximum durability for frequent heavy loads.

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• 2" SAE king pin
• Maintains hardness of 302-363 BHN
• More Than Just Parts: From snow and ice equipment to toolboxes, hydraulics, towing, truck and trailer hardware to our innovative lighting products-it's amazing what Buyers Products can do for your truck
• We Do Things The Right Way: We design products like we're building them for ourselves, because we are; Our teams are staffed with engineers and experts who know how to make a product exceptional
• Durable and Dependable: Founded in 1946, Buyers Products has become a leader in the truck equipment industry though our commitment to customer care, innovation, and value across our range of products

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Buyers Products KP20038 Forged King Pin – Balanced 0.38-Inch Plate

The Buyers Products KP20038 offers a versatile middle ground with its 0.38-inch bolster plate thickness. Like its thicker sibling, it features a 2-inch SAE forged king pin with a hardness range of 302-363 BHN, providing excellent wear resistance. This weldable king pin is ideal for trailers that see regular use but don’t require the extreme thickness of a 0.50-inch plate.

You’ll appreciate the balance of strength and weight, making it easier to handle during installation while still delivering robust performance. Buyers Products’ engineering expertise ensures this king pin meets rigorous standards, giving you confidence in your fifth wheel connection. If you run a mixed fleet or need a reliable all-around king pin, the KP20038 is a smart pick that won’t break the bank.

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• 2" SAE king pin
• Maintains hardness of 302-363 BHN
• More Than Just Parts: From snow and ice equipment to toolboxes, hydraulics, towing, truck and trailer hardware to our innovative lighting products-it's amazing what Buyers Products can do for your truck
• We Do Things The Right Way: We design products like we're building them for ourselves, because we are; Our teams are staffed with engineers and experts who know how to make a product exceptional
• Durable and Dependable: Founded in 1946, Buyers Products has become a leader in the truck equipment industry though our commitment to customer care, innovation, and value across our range of products

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ELSOON WA15 5050 Forged Steel King Pin – Enhanced Stability

The ELSOON WA15 5050 is a forged steel king pin designed for enhanced towing stability and load capacity. It features a 2-inch collar and a 3/8-inch (0.375-inch) bolster plate, making it compatible with a wide range of fifth-wheel and gooseneck trailers. The high-quality forged steel construction ensures superior strength and longevity, even in harsh conditions.

This king pin is specifically engineered to reduce the risk of unhooking during transit, improving load security for your semi trailer. The 2-inch axle collar fits standard fifth-wheel hitches, and the 3/8-inch bolster provides a solid mounting base. If you’re looking for a dependable replacement that emphasizes towing stability, the ELSOON WA15 5050 delivers solid performance without unnecessary frills.

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• Compatibility: Specifically designed for use with WA15 5050 Forged Trailer King Pins, compatible with 5th-wheel trailers for heavy-duty towing applications
• Durable Construction: Made from high-quality forged steel for superior strength and longevity, ideal for harsh, long-term use
• Specifications: 2" axle collar and 3/8" bolster plate, designed to fit a wide range of fifth-wheel and gooseneck trailers
• Enhanced Towing Strength: Provides excellent towing capacity and stability, reducing the risk of unhooking during transit and improving load security
• Easy Installation: Simple to weld onto your fifth-wheel trailer for a quick and secure installation, ensuring improved towing performance

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Buyers Products KP20025 Forged King Pin – Lightweight 0.25-Inch Plate

The Buyers Products KP20025 is the lightest option in their lineup, with a 0.25-inch bolster plate thickness. Despite its thinner profile, it still features a 2-inch SAE forged king pin with a hardness of 302-363 BHN, ensuring reliable strength for lighter-duty applications. This weldable king pin is perfect for smaller trailers or those that don’t carry maximum loads.

You’ll find the KP20025 easier to handle and weld due to its reduced weight, making it a good choice for DIY installations or quick replacements. Buyers Products maintains the same engineering standards across their king pin range, so you get consistent quality. If your semi trailer operates with lighter payloads or you need a cost-effective replacement, the KP20025 offers dependable performance without overbuilding.

View all product features

• 2" SAE king pin
• Maintains hardness of 302-363 BHN
• More Than Just Parts: From snow and ice equipment to toolboxes, hydraulics, towing, truck and trailer hardware to our innovative lighting products-it's amazing what Buyers Products can do for your truck
• We Do Things The Right Way: We design products like we're building them for ourselves, because we are; Our teams are staffed with engineers and experts who know how to make a product exceptional
• Durable and Dependable: Founded in 1946, Buyers Products has become a leader in the truck equipment industry though our commitment to customer care, innovation, and value across our range of products

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BOYISEN 5th Wheel King Pin Lock – Anti-Theft Security

The BOYISEN 5th Wheel King Pin Lock is a solid steel anti-theft device designed to secure your semi trailer when parked. Unlike standard king pin locks, it features a convenient handle that turns the cylinder outward for easier locking and unlocking. The lock uses a unique key system, so you won’t have to worry about key duplication with other BOYISEN lock owners.

Constructed from solid steel rather than cast steel, this lock is weather-resistant and hard to break. It comes with three keys and a warning tag for added visibility. If you lose your key, the 2025 batch includes a key ID printed on the key for replacement. While not a king pin plate itself, this lock is an essential accessory to protect your investment when your trailer is unattended.

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• More Convenient with Handle, Compared with other kingpin lock, BOYISEN trailer kingpin Lock add handle and turn cylinder outward instead of downward, more convenient while lock or unlock for 5th wheel
• Keyed Unique, no worry about another BOYISEN kingpin lock owner will have the same key. BOYISEN anti theft trailer lock using blossom lock, not easy to break; Come with 3 keys for your lock, so you can keep one as backup
• Heavy Duty Construction: This 5th wheel hitch lock is made of solid steel instead of casting steel, strong enough for weather resistant, hard to break. The heavy duty steel will add more difficulties for steal drills, and lasts for years
• Key Lost? No Worrying! In 2025 batches locks, there's a key ID printed on the key, please note it down or take a photo of it, provide us with the key ID to copy the key if your keys are lost
• High Visibility: This Kingpin lock is designed with a warning tag, so you could notice if it is still stay in place, and remind you of removing it when you want to hitching
• Universal Fit: ideal for trucking companies, RV dealers or fleet drivers, used for RVs, Boats and Campers Semi-Truck

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Buyer’s Guide: What to Consider

Choosing the right king pin plate involves balancing load capacity, material quality, and installation ease. Here are five key factors to consider.

• Bolster Plate Thickness: Thicker plates (0.50-inch) handle heavier loads but add weight. Thinner plates (0.25-inch) suit lighter trailers. Choose based on your typical payload.
• Material and Hardness: Forged steel king pins with a hardness of 302-363 BHN resist wear and deformation. This ensures a long service life under repeated coupling stress.
• Weldability: Most king pins require welding to the bolster plate. Ensure you have a qualified welder or choose a model that matches your installation capabilities.
• Compatibility: Standard 2-inch SAE king pins fit most fifth-wheel hitches. Verify your trailer's bolster plate dimensions and collar size before purchasing.
• Security Features: If you park your trailer unattended, consider a king pin lock. Solid steel locks with unique keys deter theft and protect your investment.

Conclusion

Selecting the best king pin plate for your semi trailer depends on your specific hauling needs. For heavy loads, the Buyers Products KP20050 offers unmatched thickness, while the ELSOON WA15 5050 enhances stability. The KP20038 provides a versatile middle ground, and the KP20025 suits lighter applications. Don’t forget the BOYISEN lock for security.

Evaluate your trailer’s weight requirements and installation preferences to make the right choice. Any of these products will strengthen your fifth wheel connection and keep you safe on the road.