This Device is for Airplane Modelers that have their Engines and Fuel Lines in "hard to get at" Places such as Cowlings. One-Piece Valve Assembly installed into Airplane with Convenient Fueling Probe for Refueling. One Pre-Assembled Fueling Valve (Glow Fuel) One Fueling Probe (DUBP2339) One Knurled Nut w/Serrated Washer Overall length (front to back): 13/16" (20mm) Mounting nut diameter (what is seen on outside of cowl): 1/4" Hole size (drilled through cowl): 3/8" Length inside cowling: 1/2" Will require drilling 3/8" hole for acceptance of valve assembly. This will ONLY work with Glow Fuel. For GAS Fueler, use DUBQ0655. ir/jl &