The O.D. at the bottom of each Conical Spring is only 1.250'' & tapers up to 1.46'' at the retainer. This is done so the springs will fit into a stock, unmachined spring pocket, yet take advantage of a larger diameter retainer. Dyno tested through 10,000,000 cycles with only a 3 lb. loss of pressure.Use with Comp Cams #249-743 (7° steel) or #249-740 (10° steel) retainers. 105# @ 1.750'' closed, 280# @ 1.250'' open, coil bind @ 1.100''.