Duckpin bowling is a variation of 10-pin bowling. The balls used in duckpin bowling are 4-3/4 in (12 cm) to 5 in (12.7 cm) in diameter (which is slightly larger than a softball), weigh 3 lb 6 oz (1.5 kg) to 3 lb 12 oz (1.7 kg) each, and lack finger holes. They are thus significantly smaller than those used in ten-pin bowling but are slightly larger and heavier than those used in candlepin bowling. The pins, while arranged in a triangular fashion identical to that used in ten-pin bowling, are shorter, smaller, and lighter than their ten-pin equivalents which makes it more difficult to achieve a strike. For this reason (and similar to candlepin bowling), the bowler is allowed three rolls per frame (as opposed to the standard two rolls per frame in ten-pin bowling).