This tool works perfectly for all the Ethernet cables I've crimped (I've not tried crimping anything other than Ethernet). The cable is held within the tool securely in position while you're crimping and I've not had any dud cables so it seems to work every time. The cable cutter on the crimper is very sharp and located near the handle so I have been a little nervous of getting a finger caught in there but that hasn't happened yet. There's also a really useful little jacket scoring tool which is similar to the cable cutter but fits cables neatly into it such that it only scores the jacket and doesn't go all the way through the cable. As for the little yellow tool supplied with it - I've found no use for that yet.