5" x 2" Cast Iron V-Groove Wheel Swivel Caster with Face Contact Brake - 900 Lbs Capacity overall-height-6-1/8 4" x 2" Forged Steel

4" x 2" Forged Steel V-Groove Wheel Rigid Caster - Part # 146FVG420R

The heavy duty cast iron wheels come with thicker treads

While ductile steel is very hard

500 Hub Length (Plain Bore): 3-11/16" Inner Wheel Diameter: 7-3/4"

Swivel Caster: 146CIRB420S Rigid Caster:  146CIRB420R

5" x 2" Cast Iron V-Groove Wheel Swivel Caster with Face Contact Brake - 900 Lbs Capacity overall-height-6-1/8 4" x 2" Forged Steel5" x 2" Cast Iron V Groove Wheel Swivel Caster with Face Contact Brake Part # 146VIRB520SFCB V Groove wheels are designed to guide equipment by rolling on inverted angle iron track, however, they can also operate while not on a track thanks to the tread on either side of the v groove. The cast iron wheel offers a strong, resilient, cost effective solution for heavy loads. If more capacity is needed, check out the heavier duty ductile steel & forged