Kaj so imperial spanner velikosti?

Velikost, kot sledi

:1/4 inch - 5/16 inch - 3/8 inch - 7/16 inch - 1/2 inch - 9/16 inch - 5/8 inch- 11/16 inch - 3/4 inch - 13/16 inch - 7/8 inch - 15/16 inch