Amazon.com: Casio GA-100L-1A G-Shock GA-100 Military Series Watch (Black / One Size) : Clothing, Shoes & Jewelry
Amazon.com: Casio Men's G XL Series Quartz Watch Strap, WR Shock Resistant Resin Color: Black and Blue (Model: GA-100-1A2CR) : Clothing, Shoes & Jewelry
Amazon.com: Casio GA-100L-1A G-Shock GA-100 Military Series Watch (Black / One Size) : Clothing, Shoes & Jewelry
G Shock GA 100 (module 5081) User manual and a VERY detailed functions overview - YouTube