The P330 YBICO Tensioner is a light duty poly banding tensioner. It can be used in 3/8" to 5/8" applications, both polyester, and polypropylene. The tensioner is a pulley mounted on a spring mechanism or adjustable pivot point that is used to keep tension on the engine belts. The tensioner holds the bottom strap while a feedwheel bites into the strap and tightens it. Tensioners for open seals are for use on flat surfaces. The P330 YBICO Tensioner is very effective.