4 blocks. Keep your RV stable, eliminating most movement and sway with the strongest jack blocks on the market. Unique design provides the most stability and strength. Perfect fit for 9" large round jack feet found on many 5th wheels and other RVs. The corner ridges keep the foot secure and stable. The shorter height (4.25") make them convenient for stabilizer jacks, compared to the bucket block. 10,000 lbs. capacity. The larger surface area created by the web design on the bottom of the block is a more stable surface area than alternative blocks. Size: Recessed pad area is a 9.25" circle with a 5.25" gap between ridges. The block is 10.5x10.5x4 and weighs 6.8 lbs. The block is made in the USA of UV-resistant recycled plastic. Patent pending design by American engineers. These heavy duty blocks are made the old fashioned way, and are built to last. Case of 4 blocks. The OX BLOX MAXX Trailer Jack Block is designed specifically to fit the 9" round RV drop legs found in most 5th wheel trailers. They are made in the USA of 100% recycled plastic and are UV resistant, making them the kind of block that will last a lifetime. Each block is 4" tall and is stackable so you can get 8" of height or more without losing any weight capacity. Each block weighs about 6.8 lbs. If you're searching for a block for your RV, camper, trailer, 5th wheel, toy hauler, or motor home, the OX BLOX MAXX is a great choice. DURABLE: OX BLOX Trailer Jack Blocks are professionally engineered and are as strong as an ox. They are made in the USA from recycled plastic and are UV and temperature resistant. They are made to last. VERSATILE: This is the perfect block for camp trailers, 5th wheels, boat trailer, horse trailers, or anything else that needs support blocks. It is 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. 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.