The OX BLOX Trailer Jack Block is the strongest trailer support block on the market. You wont find anything else that's stronger, more durable, and more versatile than OX BLOX. Durable â The OX BLOX Trailer Jack Block is professionally engineered and is as strong as an ox. It's made in the USA from recycled plastic and is UV and temperature-resistant. Versatile â This is the perfect block for camp trailers, 5th wheels, boat trailers, horse trailers, or anything else that needs support blocks. It's designed to fit pad jacks, post jacks, stabilizer jacks, wheel jacks, and more. You can even stack them on top of each other and use them to support the frame. Stable â It works well on virtually any surface including gravel, grass, dirt, and pavement. Unlike other blocks, OX BLOX will hold stable in a variety of circumstances.• Supports nearly any tongue jack, post, foot, or stabilizer (round or square)• 10, 000-lb. capacity• Stackable• Made of 100% recycled plastic• UV-resistant• Measures: 12"L x 9-3/8"W x 6"H• Weight: 8.9 lbs. UV and temperature-resistant Designed to fit pad jacks, post jacks, stabilizer jacks, wheel jacks, and more Blocks can be stacked and used to support the frame | OX BLOX Trailer Jack Block, Each Made in USA