Willi Footwear

Size Guide

The bases will vary slightly. It is best to measure your foot or an old pair, from the center of the heel, to the top of your big toe.

Please always check your size before ordering as you will incur postage fees should you need to swap for a different size.


Do you have really narrow or really wide feet?
Smaller or larger sized straps can be added to different sized bases. This means you can customize your fit to perfection!
Slim straps can be added to the corresponding Men’s / Unisex base and vice versa.
Get in touch if you need help choosing your size.


The Boomerangz size range is based on the MEN’S US size range. Although they are UNISEX (it says UNISEX on the base) – This means that if you are ordering a ladies slim style and you are normally a 9, you will need to order a 7/8 instead. If you are normally a 7/8, you will need to order a 6 and so on… best to measure your foot or an old pair and use the sizing charts provided  🙂





  1. Click on the link below of your desired size
  2. The PDF will open in a new window
  3. Click FILE then click PRINT
  4. Make sure PAGE SCALING is set to NONE
  5. Place your foot in the outline to see if that is your correct size
  • US Slim 4/5 — 235mm — 9.25 inches L — 3.93 inches W
  • US Slim 6 — 247mm — 9.72 inches L — 3.74 inches W
  • US Slim 7/8 — 260mm — 10.24 inches L — 3.85 inches W
  • US Slim 9 — 272mm — 10.71 inches L — 3.93 inches W
  • US Slim 10/11 — 286mm — 11.26 inches L — 4.05 inches W