"FED STD NO. 66, SAE 1020;7.250 IN. MIN AND 7.254 IN. MAX DIA APERTURE, 0.281 IN. THICK MATERIAL; BODY OF ADAPTER OFFSET, 1.625 IN. HIGHT;ADAPTR TO DRUM MOUNTED WITH 10 UNTHREADED HOLS, 0.462 IN. MIN AND 0.467 IN. MAX DIA QUALLY SPACED ON 14.875 IN. BOLT CIRCLE; ADAPTER TO HUB MOUNTED WITH 10 UNTHREADED HOLES, 0.880 IN. MIN AND 0.890 IN. MAX DIA EQUALLY SPACED ON 11.250 IN. BOLT CIRCLE"