This 4" x 1-1/4" Polyurethane on polypropylene Caster is an exemplary caster for those who must carry weight loads with immense ergonomic ease while also rejecting debris and reducing interruption caused by failed casters and flawed flooring. Polyurethane caster wheels operate so astonishingly well during pushing and pulling because they feature polyurethane tread of the industry-standard, chemically bonded to a polypropylene core.