At first I thought it is a useless stuff to purchase because every guitarist knows which cable belong to him. But later on I sussed out that it is bloody good way to identify my cables as I have massive amount of cable going between the pedalboard, amps and my rack box. So now I know that this cable is between the pedalboard and my Marshall JCM900. I installed it on a Neutrik NP2 X-B which is a straight jack plug, and I also managed to fit on a angled Neutrik NP2 RX-B plug but they are not really compatible with each other...so it is not a perfect fit. (but with a small force I could do it right :D )
I am using these colour rings for my guitar cables. Very good aplication, can not fall off, very easy to see in the dark and great colour. I have 4 of these in a flex hose, so this makes a lot easier to know which is what.