Hold Fitting Set, Air, Use To Apply Air Pressure To Keep Valve Closed While Replacing Valve Spring, For Use With 912, 915, 2078, 3087, or 3271 Valve Spring Compressors, Material Steel, Number of Pieces 2, Includes 14mm x 1/4 In NPT Thread Air Hold Fitting, 18mm x 1/4 In NPT Thread Air Hold Fitting