 Forty-nine target marbles are grouped closely together in 6 foot diameter (1.8 metre) raised concrete ring covered with sand, each of the target marbles being a coloured glass or ceramic sphere having a diameter of approximately 12mm (half an inch).Two teams of six players of any age, gender or skill level, take turns using the tip of the finger to aim and project the "tolley", a larger marble (commonly referred to as the "shooter" or "taw"), which is a glass or ceramic sphere of 18mm diameter (three-quarters of an inch), deploying top spin, back spin and side spin, to drive other marbles out of the ring.A player's knuckle must be touching the ground when shooting, known as "knuckling down".