Dual Wheel Hooded Casters, B Stem, 1.5" Caster, Black. Strength and high performance make these replacement casters an excellent choice for most Alera® seating. Weight rated 100 lb. per caster wheel. Caster/Glide/Wheel: Grip Ring Stem Twin Wheel Casters; Color: Black; Stem Type: B; Wheel Tread: Hard.