The drive size is the square opening on the back of a socket that connects to your ratchet, extension or breaker bar. Teng Tools covers the full range:
1/4" drive — small fasteners, electronics, trim, tight spaces. Typical sockets 4–14 mm.
3/8" drive — the everyday all-rounder for automotive work. Typical sockets 8–22 mm.
1/2" drive — suspension, wheels, higher-torque work. Typical sockets 10–36 mm.
3/4" and 1" drive — trucks, agriculture, industrial equipment.
The drive size of the socket must match the drive size of the ratchet — or use an adaptor. Every Teng socket lists its drive size in the product specs.
Impact sockets (for use with impact guns) are a separate range — they're made from a tougher steel and are usually black. Never use standard chrome sockets on an impact gun.