I went for small, I usually buy medium. Im sort of slim-ish with a developing gut. I just wrapped a tape measure round my chest across the nipples and added 2 inch (like all men do
).
Fit is not too tight or too loose. Just ordered the insoles and controller now, it has a little connector in the body warmer to connect the insoles.
Really easy to wire up too. took 10 min.
used the size guide from the website.
INCHES 38 40 42 44 46 48 50
KEIS SIZE XXS XS S M L XL XXL