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. 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. The OX BLOX MAXX is designed specifically to fit the 9" round RV drop legs found in most 5th wheel trailers and some motor homes and bumper-pull trailers.• Fits 9" round feet and smaller• 10, 000-lb. capacity• Stackable• Made of 100% recycled plastic• UV-resistant• Measures: 10.5"L x 10.5"W x 4"H• Weight: 6.8 lbs. Made in the USA from recycled plastic UV and temperature-resistant 10, 000-lb. capacity | OX BLOX MAXX Trailer Jack Block, Each Made in USA