The EX is a series of lens made by Sigma which is considered its higher range. Like the L lens of Canon. To differentiate the EX series from the rest of the consumer lens, Sigma uses a logo with the word EX on it and coats the barrel of the lens with a velvety, rubbery surface. When a EX lens is new, the coating gives a good grip to the lens (subjective). However, after some years of usage and basic wear and tear, the coating will start to peel off revealing the smooth lens barrel below. Some EX coating seems to be very prone to peeling.