Clutch Rotor 2.87" OD with a 3/4" ID, the 3/16" key is made into the part. Use a 3" ID clutch drum.
Over all height is 1.15".
Shoe width is .732"
This clutch rotor can be used with the Drum listed below:
Clutch Drum 3" or 76.2 mm ID with 1/2-20 threads
http://www.staton-inc.com/store/products/Clutch_Drum_3_or_76_2_mm_ID_with_1_2_20_threads-799-0.html