Our sizing is based around average, reasonably fit people. It should match the size you'd choose on the high street, not a cycling racing brand. Brands tend to have wildly varying size policies. Ours is "real".

 

CHEST INCHES CHEST CM
XS 34-36" 88-91cm
S 36-38" 91-96cm
M 38-40" 96-101cm
L 40-42" 101-107cm
XL 42-45" 107-114cm
XXL 45-48" 114-122cm

 

Our tops have a "casual fitted" cut. They're looser, but more fitted than non-cycling fashion tops.
CHEST:
Measure around the fullest part of your chest, keep the tape level, under your arms and breathe naturally. Don't tense!