The first dimension quoted refers to the width of the sheave, the second to its diameter.
£3.55 – £31.55
For larger sheaves to be used with thin rope use wire sheaves.
These are often handy as through-mast halyard sheaves, using normal” rope.
11 x 25mm, 11 x 30mm, 11 x 35mm, 11 x 40mm, 11 x 50mm, 11 x 60mm, 13 x 50mm, 13 x 60mm, 13 x 70mm, 13 x 80mm, 15 x 100mm, 15 x 90mm, 16 x 70mm, 16 x 80mm, 18 x 100mm, 18 x 90mm