Rubber protects vinyl or laminate flooring from scratches. The wheel tire is softer, non-marring silicone appropriate for rolling on a hardwood floor. Shelf top roller on track design maintains maximum vertical and horizontal shelf stability.

They roll effortlessly and very easy to install. Aligning the mounting holes to use a single bolt (versus a screw on each side) takes a steady drill hand. Fit wood crib as replacement for old. Worked very well.