USR 400 fits the widest range of cable sizes. USR 401 fits the widest range of Romex® and other flat cable sizes. Captive screw forces the locking flap against the cable. Captive screw meets typical European requirements wherein the Strain Relief device must remain attached to the panel during cable removal or replacement. Nylon USR 400 & 401 comply with: - IEC Publication #335 - CEE #10 and # 11 Easy installation: fingertip pressure locks bushing into .875" (22,2 mm) diameter holes with panel thickness up to .125" (3,2 mm). Reinforcing ribs for extra strength. Bell mouth contour, radiused at 1.5x the exit hole diameter, eliminates the need for a separate cord guard. Protect cables against forces of pull, push, twist, and flex. Heyco-Tite Liquid Tight Romex Connectors. For Double D Mounting Hole Punches, click here.