This lightweight harness is specifically designed for the Foil Assist battery box. It is made from ultra-soft molded EVA for comfort and added buoyancy. It features a low profile with a tapered waist for freedom of movement, lumbar support to keep it in place while riding, a D-ring attachment for your leash, and a neoprene waist belt with a Fidlock magnetic buckle for security and quick release. If you need to replace your current eHarness due to wear and tear but your battery box is still in good condition, you only need this spare part. For the correct battery box mounting process, please refer to the help center . Sizes: S – M (WAIST MEASUREMENTS: 71 – 89 CM / 28" – 35") L – XXL (WAIST MEASUREMENTS: 89 – 114 CM / 35" – 45")