Boilies are a selective carp bait. Made from various types of meal, flavor extracts, and scent additives. They are most commonly found in a round shape, but you can also come across boilies in the form of barrels, then they are called "dumbells" :) The size of the boilies depends on the angler's preference as well as the fish and ranges from 6 to 35 mm. The most commonly encountered and used size is 18-20 mm. The size of the boilie makes it a more selective bait than most available on the market, simply because smaller fish cannot swallow such a large bait.