Wrench drive side fits 10mm, 12mm, or 17mm wrench or socket. Ball Detent holds the bit into drive unit. 12 PC. Sets include sizes: SAE 1/8, 9/64, 5/32, 3/16, 7/32, 1/4, 5/16, 3/8, 7/16, 1/2, 9/16, 5/8. Metric 2.5mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 12mm, 14mm, 17mm