F320 Grinding Wheel Adapter ~ This is used in cylinder of US standard grinding machines. ~ Hardened and ground. ~ For 1-1/4" I. D. grinding wheels. ~ Wheel width capacity is 1/4 to 3/4". ~ 1" diameter at the large end of the taper hole. ~ Made in Taiwan. ~ Sopko style. ~ Left hand threads. ~ Thread is 1-1/4"-16 LH. ~ Hardness is 20-25 HRC.