Dee Zee vented gas cap is an exact replacement of the gas cap that comes with all Dee Zee tanks. Vented to alleviate pressure from vapor build up. Replacement cap portion requires existing threaded neck for venting. Transfer tank service part Vented gas cap only Replaces Dee Zee transfer tank cap (excludes threaded neck) Alleviates dangerous build up of vapor Sold individually MODEL NO - DZGASCAP2