
Because of the sheer weight of numbers, square drives are still measured in imperial units, the most common are listed below. There are also 5/16" for screw bits only, 1" and more for trucks etc.
1/4"
-37%

Amazon.co.uk
5.0
£23.25 £37.15
Draper Expert 18 Piece Metric Socket Set | Ratchet Tool and Case | 3/8" Square Drive | HI-TORQ MM/AF Sockets | DIY Home Professional and Car Kit |Hand Tools...
3/8"
-5%

Amazon.co.uk
5.0
£22.50 £23.72
Draper 1/4" 47 Piece Square Drive Metric Socket Set | Micrometre Reversible Hand Tool |Soft Grip Ratchet | 21 Metrics Sockets Mechanics Car Tools |...
1/2"

Amazon.co.uk
5.0
£15.97
CASOMAN Oil Drain Plug Key Set, 1/2" Drive, 8mm, 10mm, 12mm, 14mm, 1/2", 3/8", 6PCS Oil Service Socket Set, Internal Square