I got tired of always needing to pull out a screwdriver to drain the bowls and the thumb screw drains made commercially are only for the pre77 carbs. Materials wise this cost me about $3.50 because I had all the tools. These are 3mm Stainless thumb screws that are threaded into a tapped drain screw with loctite. Long term dependability is yet to be determined but I have high hopes. Love to hear some feedback/ suggestions.