had 5/4 /2 rollers on my 2 x 72 belt grinder , bought this as an upgrade . took 5 minutes to replace my 5" drive roller with this 6" roller .am thrill with the increase in belt speed !!! by all accounts and my best math this increased belt speed by 1000 feet per minute . the differance was immeadiately apparent ! wow , massive improvement for 50.00 .