The Andersen Hitches Trailer Jack Block eliminates nearly all the movement in your parked RV or trailer. You will be amazed how solid everything is! For best results, use one Trailer Jack Block on each stabilizer jack. Using the Trailer Jack block under your jacks means they don't need to extend down as far, saving on wear and tear over time. And because the jack doesn't need to extend fully, there's less stress on it from movement - it's a win-win for RVs and Trailers (and your pocketbook)! Simply attach the Trailer Jack Block to the bottom of your stabilizer jack using the built-in magnets and hit 'auto-level'  theres no need to check and adjust each block! It is extremely fast and convenient! The Trailer Jack Block is also strong and durable and resists dirt. The blocks are stackable for extra height and can even double as seats or stepstools. The Trailer Jack Block from Andersen Hitches comes with a LIFETIME WARRANTY (just pay shipping). It's built tough, built to last, and rated at 6,000 lbs. Dimensions: 8" tall, 12" dia. base, 10" dia. top (14" tall when double-stacked). Recessed pad area is 9-1/8" diameter, recessed post-hole is 2-1/2" diameter. Each block weighs 5.5 lbs.