M General for height 155 - 161CM ( chest strap maximum range 89 cm )<br /><br />L General for height 162 - 166CM( Maximum range of 92 cm chest strap )<br /><br />XL general for height 166 - 172CM( Maximum range of 96 cm chest strap )<br /><br />XXL generally suitable height 166 - 172CM( Maximum range of 100 cm chest strap)<br /><br />XXXL generally suitable height 172 - 180CM( Maximum range of 104 cm chest strap)