Bauer TUUK Light Speed 4 EDGE Senior Stainless Steel Replacement Steel (Pair) (9) Size Chart is as follows:12=306, 11=296, 10=288, 9=280, 8=272, 7=263, 6=254, 5=246, 4=238, 3=221 The size steel you need will be a 3 digit number on the white holder. This can be seen by looking down from the blade side.