10th Planet rash guard

Evening to those in the UK, afternoon to the USA.

I'm thinking of ordering a grey 10th planet rash guard from Melee, but wanted to check on the correct size. The reason I ask is I currently have a Hunter long sleeve and an Atama short sleeve which are both size small and are slightly too tight. However my Sprawl long sleeve is also size small but is quite baggy! How do the 10th Planet sizes compare to Sprawl, for example?

im 6ft slim build and about 180lbs small is a perfect tight fit med is slight bigger but still is kool. i where both