TXTLED-FLCA-Freightliner Century, Columbia & Coronado Sleeper Amber LED with Base (35 Diodes)" 3 wire 2 function

With your arms relaxed at your sides, measure around the fullest part of your chest.

Measure around the narrowest part of your natural waist, generally around the belly button. To ensure a comfortable fit, keep one finger between the measuring tape and your body.