Hi That is what I said. The disk with 20 bands would work for both a 360 RPM and 60Hz light or a 300 RPM and 50 Hz light. Tony mentioned that one could increase the number of bands for the problem of the 50Hz with a 360 RPM drive. It makes sense. A strobe disk with 50 bands would work for this problem. One could multiply the number of bands by any integer and it would still work. Multiplying 16.667 times 3 gives a nice integer value of 50. Tony mentioned that most 8 inch drives were speed controlled by the mains and as long as the belt was in good shape, using a strobe wasn't much needed. Yaers back, a friend and I were able to aquire drives that were setup for 50Hz 220V. We wanted to use these with a put together Series II Intel machine. We're 60Hz 115V here. We put a strobe disk on the flywheel and took a flat file to the motor pully. About 20 mintes of grinding brought the drive to the right speed. The voltage was solved by a buck transformer created from some universal transformers we got from some surplus supplies. Dwight _________________________________________________________________ Share life as it happens with the new Windows Live.Download today it's FREE! http://www.windowslive.com/share.html?ocid=TXT_TAGLM_Wave2_sharelife_112007