Galaxy Watch 4 Band Size: They All Take 20mm Bands
Amazon.com: HSWAI 10 Pack Compatible with Samsung Galaxy Watch5/4 Band 40mm 44mm/Galaxy Watch5 Pro 45mm/Galaxy Watch 4 Classic 42mm 46mm Silicone Sport Bands Replacement Strap for Women Men (Large) : Cell Phones
Samsung unveils Tizen-powered Galaxy Watch in 42mm and 46mm sizes - GSMArena.com news