All Standard Retainers are made from Aerospace Spec Aluminium and are Anodized to MIL-SPEC Type 2 Class 2 (Red)
Each Retainer fits (nests) inside the next size up. So.....
29mm will fit into a 38mm Retainer
38mm will fit into a 54mm Retainer
Please note : Cones will not nest in each other, but Standard Retainers will nest in Coned Retainers
98mm Standard Retainer & Thrust ring
Regular retainers come in sizes 29mm to 98mm