Manufactured specifically to accomidate 14/3 STW Cable NOM. O.D. 0.540" (13.7mm) - NOTE: Similar GFCI's will not FIT this larger type of CABLE (14/3 STW) AUTO RESET User Attachable - UL943 Listed 15 AMP 120 Volt Replacement GFCI Plug Unit for Portable Spas Detailed Replacement Instructions Included With Each Unit Custom made for INTEX, BESTWAY, NORDIC, and BALBOA Water Spas & Pumps Self-Testing unit per UL GFCI STANDARDS FOR LARGE DIAMETER 14AWG STW 600V Cable Only 15AMP 120VAC User Attachable GFCI WBGF18-3P-L - Replacement GFCI Plug for Spas and Power Washers This AUTO-RESET version will not require manual reset by user to re-power/re-energize after power loss. Manufactured specifically to accomidate 14/3 STW Cable NOM. O.D. 0.540" (13.7mm) - NOTE: Similar GFCI's will not FIT this larger type of CABLE (14/3 STW)