EACH GARMENT MANUFACTURE IS UNIQUE, AND THE SIZING COMPARISON MAY NOT BE EXACT. HOWEVER YOU CAN USE THESE GENERAL SIZE CHARTS TO HELP GAUGE YOUR SIZE IN EACH OF THE SIZING SYSTEMS. 
(ALL MEASUREMENTS ARE IN INCHES)

TOPS

STAMP L/S
WIDTH: S - 18.5 / M - 20.5 / L - 22.5 / XL - 24.5 / XXL - 26.5
LENGTH: S - 27 / M - 28.5 / L - 30 / XL - 31.5 / XXL - 32.75
SLEEVE LENGTH: S - 23 / M - 24 / L - 25 / XL - 25.5 / XXL - 26 

RETRO TILT T-SHIRT
WIDTH: S - 19.5 / M - 20.5 / L - 21.5 / XL - 23 / XXL - 24.5
LENGTH: S - 27.5 / M - 28.5 / L - 29.5 / XL - 30.5 / XXL - 31.5
ARCH L/S
WIDTH: S - 18.5 / M - 19.5 / L - 21.5 / XL - 23 / XXL - 25
LENGTH: S - 26 / M - 29 / L - 30 / XL - 31.5 / XXL - 32.5
SLEEVE LENGTH: S - 26 / M - 27 / L - 29 / XL - 31.5 / XXL - 33.5
3M SPLIT HOODIE
WIDTH: XS - 19 / S - 20.5 / M - 21.5 / L - 23 / XL - 23.5
LENGTH: XS - 26 / S - 27 / M - 28 / L - 29 / XL - 30
SLEEVE LENGTH: XS - 31 / S - 32.5 / M - 33 / L - 36 / XL - 37
APB COLLAB T-SHIRT
WIDTH: S - 18 / M - 20 / L - 22 / XL - 24 / XXL - 26
LENGTH: S - 27 / M - 29 / L - 31 / XL - 32 / XXL - 33
STAMP T-SHIRT
WIDTH: S - 18.5 / M - 20.5 / L - 22.5 / XL - 24.5 / XXL - 26.5
LENGTH: S - 27 / M - 28.5 / L - 30 / XL - 31.5 / XXL - 32.75
MESH PANEL 1/4 ZIP
WIDTH: S - 23 / M - 24 / L - 25 / XL - 26 / XXL - 27
LENGTH: S - 27 / M - 28 / L - 29 / XL - 29.5 / XXL - 30
SLEEVE LENGTH: S - 34 / M - 35 / L - 36 / XL - 37 / XXL - 38
YEAR ONE L/S
WIDTH: S - 35-37 / M - 38-40 / L - 41-43 / XL - 44-46 / XXL - 47-49
LENGTH: S - 28 / M - 29 / L - 30 / XL - 31 / XXL - 32
SLEEVE LENGTH: S - 34 / M - 35 / L - 36 / XL - 37 / XXL - 38
PREMIER T-SHIRT
WIDTH: S - 18 / M - 20 / L - 22 / XL - 24 / XXL - 26
LENGTH: S - 27 / M - 29 / L - 31 / XL - 32 / XXL - 33
3 PANEL HOODIE
WIDTH: S - 20 / M - 22 / L - 24 / XL - 26 / XXL - 28
LENGTH: S - 26 / M - 27 / L - 28 / XL - 29 / XXL - 30
SLEEVE LENGTH: S - 33 / M - 34 / L - 35 / XL - 36 / XXL - 37

BOTTOMS

SPLIT NYLON SHORT
WAIST (NOT STRETCHED): S - 30 / M - 32 / L - 33 / XL - 34 / XXL - 36
FRONT RISE: S - 11.75 / M - 11.75 / L - 12 / XL - 12.75 / XXL - 12.75
INSEAM: S - 5.5 / M - 5.75 / L - 6 / XL - 6.25 / XXL - 6.5
UTILITY CARGO PANT
WAIST: S - 29-30 / M - 30-31 / L - 32-33 / XL - 36 / XXL - 38
FRONT RISE: S - 11.5 / M - 12.5 / L - 13 / XL - 13.5 / XXL - 14
BACK RISE: S - 16 / M - 16.5 / L - 17 / XL - 17.5 / XXL - 18
LENGTH: S - 29.5 / M - 30 / L - 30 / XL - 31.5 / XXL - 31.5
CARGO TRACK PANT
WAIST: S - 28-30 / M - 31-32 / L - 33-34 / XL - 35-36 / XXL - 37-38
LENGTH: S - 40 / M - 41 / L - 42 / XL - 43 / XXL - 44