The Britool open-end spanners (imperial) are forged in chrome vanadium steel with a high chrome finish. The open end is angled at 15° from the handle axis.

ASME B 107-100.

The Britool BRIE113289B Open end spanner has the following dimensions:
Size: 1/4 x 5/16 AF
Length: 122mm
Weight: 20g
Height: 3.30mm