High speed hydraulic clyinders filled with biodegradable fluid lift or launch your boat in 24 SECONDS. Cylinders are fully closed when in the up postion (which is 95% of the time) protecting them from scale build up and zebra mussels. Swivel carpetd bunk supports adjust to your boat hull. Automatic shut-off valve if unit should ever lose pressure locking lift from dropping down. Adjustable legs 4' long standard in each corner (extensions optional).