This replacement 3.18mm (1/8") collet is used in these micromotor handpieces:
H.MH-170
H.MH-150 with serial numbers 811xxxx and higher (that's serial number 811 plus four more digits)
H.MH-145, H.MH-145A and H.MH-135 discontinued handpieces
Home/Foredom/Flex Shaft Maintenance/Spare Parts/Collets For Foredom Rotary Micromotor Handpieces In Kits: K.1070, K.1030, K.1050 And More