Will most .12 to .18 - Please see details below before ordering. To work with the backplates we have listed in our shop. Suitable to work with most cordless drill. The starter rod hex size is 5mm across the flats on one end. On the other end this has a ball with pin end (similiar to a drive shaft) to fit the backplates we sell. This will work with our electric starters. Please check your manual for part codes or contact us if you are not sure.