Our UL-36 lug is wax cast steel, for standard sized keys. Popularly used on Hawken and similar Plains rifles, the slot measures .53" x .12". It fits our favorite KEY-36-B or I as cast. Some gentle peening can compress it, to hold thinner keys snugly. The as-cast sprue must be removed from the base, which measures .56" wide. The dovetail is about .73" long. Mount it to the bottom of the barrel in a 0.050" deep dovetail.