Oajen 4" 100mm twin wheel caster, furniture wheel, 7/16" x 7/8" 11mm x 22mm grip ring for office chair, pack of 5 4" 100mm heavy duty twin wheel caster for office chair. Fits most chairs with 7/16" 11mm diameter caster hole. 4-7/16" mounting height. Large wheel diameter provides better mobility and good for large person. The wheels are riveted onto caster body for better wheel retention when running over cords or thrsshold. Other 100mm 4" caster may not have this feature. Exceeds BIFMA quality. Made in Taiwan.