This is a tub and shower door roller assembly used on frameless glass shower doors. It has an oval edged 3/4 in. nylon ball bearing roller attached to an aluminum bracket. Assembly clamps onto the top of the shower door glass with a vinyl glazing gasket. Will fit up to 1/4 in. thick glass. Silicone adhesive may be required on some glass panel designs. The nylon roller height is adjustable by sliding the roller up or down in the diagonal mounting slot and then tightening.