5901 size

Chest  Measure the chest around the fullest part, placing the tape close up under the arms making sure the tape is well up at the at the back over the sholder blades.
Waist   Measure around the natural waistline over any under garments which may be worn.
Sleeve  This is taken from neck center point, along the shoulder line and down the outer sleeve to the cuff edge.
Back Length Measure just under collar seam to the bottom of the garment.
5901 REG   M L XL 2XL
CHEST   48 52 56 60
WAIST   46 50 54 58
BACK LENGTH   32.5 33 33.5 34
SLEEVE LENGTH CENTER BACK   37 38 39 40
           
5901 TALL   LT XLT 2XLT 3XLT
CHEST   52 56 60 64
WAIST   50 54 58 62
BACK LENGTH   35 35.5 36 36.5
SLEEVE LENGTH CENTER BACK   39.5 40.5 41.5 42.5
           
5901 BIG   3XLB 4XLB 5XLB 6XLB
CHEST   64 68 72 76
WAIST   62 66 70 74
BACK LENGTH   36 36.5 37.25 38.5
SLEEVE LENGTH CENTER BACK   40.25 41.75 43.25 44.75