The rivets differ by the diameter of the head as well as the length of the rod. The longer the stem, the more the material to be riveted (such as leather) can be thick. The tubular rivets are made of stainless brass of silver color and give a neat appearance by where they are placed. Prym offers tubular rivets that can be used with the Creative Tool vario and the appropriate tool play. 12 tubular rivets of diameter 7.5 mm for 3 to 4 mm tissue thickness. Tubular rivets for riveting in thicker materials such as the leather ie stainless use with Vario Creative Tool (390903) Tools for Tubular Rivets Prym available separately: 673128