... precise micro bearing; 2. Zinc alloy main support with chrome plated; 3. Elegant design and rust resistance. ... Zinc alloy;Roller dimension: 21mm---25mm;Profile type: Round type, V type, U groove type,etc.Item NoMain Support MaterialsSurface treatmentUsageRS10087Zinc AlloyChrome ... steel. 2. Rollers can be 22-26mm, with V type, round type, U groove type, etc. RS series nylon shower door roller