S-WH-4DB Hamilton Series WH Workhorse Caster. Drop forged steel swivel caster construction includes a 3/4" diameter integrally forged steel kingpin (guaranteed for life!), and a precision secondary load bearing. CNC-Machined 2-9/16" diameter raceway with 3/8" hardened and polished steel balls. 3/4" precision tapered thrust bearing counteracts radial thrust. Ball check lubrication fittings in swivel assembly and in wheel hubs with tapered or straight roller bearings.