Driving system Mechanical Caliber F8F64 Average daily difference +15 seconds to -5 seconds (static accuracy)* Driving time 60 hours or more Case Material Stainless steel (SUS316L) Glass material (front) Sapphire crystal (sar coating) Glass Material (Back) Sapphire crystal Luminous Light Yes Band Material Nylon Band Width 21 mm Wrist circumference length 150mm~190mm Inside Closure Push-fold tri-fold Weight 112g Diameter 50.0mm Width diameter 42.3mm Thickness 12.4mm Water Resistance Enhanced waterproofing for daily life (10 atm) Magnetic resistance JIS Class 1 (4800 A/m min.) Other features Automatic winding (with manual winding), second hand stop device, see-through back, 24 jewels, screw-type crown, power reserve indicator