FluidMaster # 6102 2 Bolt & Gasket Tank To Bowl Kits. Includes 2 Each 5/16" x 3" Brass Bolts, Red Sponge Rubber Gasket, 4 Brass Washers, 4 Rubber Washers & 2 Each Hex & Wing Nuts. Gasket Fits Over Both Round & Hex Shaped Flush Valve Nuts.
eBay