80% of our customers should get an SR. Our best advice is to go with a model within the Series SR. Series SR flex shaft motors are 1/6 HP, run in forward and reverse at speeds up to 18,000 RPM, and offer all of the power and speed needed to accomplish most every job. Keep in mind that our motors are rated at continuous duty or maximum efficiency and NOT maximum output. If weadopted themax output ratingused by other manufacturers, it wouldqualify as 1/5 or 1/4HP. Series SR motors come in 115 Volt and 230 Volt (for use where 115V is not available). Two Year Limited Warranty on Motor and Control. M.SR Motor is a hang up motor with a standard 39? long key-tip shaft for connecting to any of Foredom’s interchangeable, quick disconnecthandpieces. Additional Motor Details: The 1/6 hp, ball bearing Series SR has 33% more power than our older 1/8 hp motors, and 66% more than our original 1/10 hp models. The added power helps to reduce stalling or slowing down under normal workloads. Advantages of Running in Reverse: Left handed users have more control of the cutting tool Reverse helps to keep dust and other debris flying away from right handed users Alternating motor direction helps to extend the life of certain abrasives Reverse helps with accomplishing symmetrical grinding and carving techniques Reverse makes it easier to back out stuck drill bits Alternating motor direction makes it easier and faster to polish metals