【Compatibility】SIZE ONE is for Series 1/2/3/4/5/6/7/8/SE/SE2 38mm/40mm/41mm model [Fitting range 6.3''-8.3'']. SIZE TWO is for Series 1/2/3/4/5/6/7/8/SE/SE2 42mm/44mm/45mm models [Fitting range (L=6.7''-8.9'')(XL=8.9''-9.9'')]. SIZE THREE is for Ultra Series 49mm model [Fitting range (L=6.7''-8.9'')(XL=8.9''-9.9'')]..【Rugged Material】It is made with soft nylon material which also has rugged and anti-scratch features. The connector is made of stainless steel which is really durable..【Wearing Design】It is designed with high quality. The hook&loop clasp method will make it easy to adjust your strap. [Max weight limit 125KG].【Breathable Design】The band is woven loop design which is conducive to sweat and heat dissipation..【Patent & Service】Patent pending [Application # 29/789,461]. We support 30-Day 100% Money Back Guarantee and 1 Year Replacement Warranty.