 Darts can range in size from about 30 millimetres ( 1 @.@ 2 in ) long in the larger snail species , down to about 1 millimetre ( 0 @.@ 04 in ) in the smallest snails that have darts . Typically most darts are less than 5 millimetres ( 0 @.@ 20 in ) long , but they are substantial compared with the size of the animal . 
