Three versions. Each one has two files named 01 and 02. The model B is plain and the nuts stand above plastic. The model C can hide the nuts. The model "C mosq" has a hole to attach a carabiner. You should use to attacha a pair number of keys or attach two groups with similar thickness. You will need: 2 M3 locknuts2 washers2 M3 allen bolts Better with inox alloy. To measure the bolts for standar keys approximately: (2.4mm · keys) + 8mm Five keys will need a 20mm M3 bolt.