Abstract: An animal tag comprising, a penetrating component (3) having two ear penetrating members (9) joined by a strip of intermediate material (13), a complementary component (15) having a locking portion (17) for each penetrating member, and ramp means (21) for each locking portion, wherein the arrangement is such that the ear penetrating members are designed to be passed through the ear (33) of an animal and to lock onto the locking portions to sandwich the ear in a gap (28) between the penetrating component and complementary component and the ramp means are arranged to co-operate with the skin penetrating members to vary the size of the gap whereby to provide a range of gap sizes to accommodate varying ear thicknesses and/or growth of the animal.