EFINEHOME Efine 6 Pack Socket Screw Bulbs Edison Retro Pendant Lamp Holder Trap Black Twist and Lock E26 E27 Socket Replacement Ring(Black) 6x Lamp Shade Ring Adapter E26/E27 Lampshade Light Shade Collar Ring Adaptor 1.58 inches(40mm) Overall; 1.58 inch(40mm) inside diameter, 2.25 inch(57mm) outside diameter This ring is only meant for certain lampholders - it will not fit all E26 threaded lampholders Warning:For your safety, please let professional electrician install to prevent electric shock