Wetsuit thickness, written as two numbers like '4/3mm', indicates the neoprene thickness on the torso (4mm) and the limbs (3mm) — thicker neoprene on the core for warmth, thinner on the limbs for flexibility. Thickness is matched to water temperature: a 3/2mm suits temperate water (~17-21°C), a 4/3mm cooler water (~14-17°C), and 5/4mm or thicker (plus boots, gloves and a hood) for cold water below ~11°C. A wetsuit works by trapping a thin layer of water that your body heats; the right thickness keeps you warm enough to surf comfortably and safely.
Key points
- Two numbers = torso/limb thickness in mm
- Matched to water temperature
- 3/2mm temperate; 5/4mm+ cold water
- Thicker = warmer but less flexible