What it is
A wafer is a hookbait with buoyancy — not a pop-up, not a stone. Hair-rigged on a short method hooklength it sits in or just over the mix, easy to suck. That is why they replaced a lot of corn on UK commercials.
Match size to the fish: 8mm for F1s, 10–12mm for carp on many day-tickets. Colour is fashion; the sink rate is the fishing.