Types: Steel on steel: The inner and outer rings are composed of hardened and phosphated bearing steel and the spherical sliding surfaces are treated with a running-in lubricant. Steel on bronze: The inner rings are composed of hardened bearing steel and the outer rings of bronze. Stainless steel on bronze: The outer rings are composed of stainless steel (Material no.: 1.4418) with holes for mounting the inner rings which are composed of aluminium bronze (Material no.: 2.0975).