RJ11 is a standard size/type so that one will be fine. You could pick one up at your local maplin for less money if you don't need 50

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The fun part is to attatch the connector you need a crimping tool - see 'customers also bought' in your link.
Once you have the tool you just lay the wires out in the same order as in the existing cable, cut them to the same length and slide them in to the connector then squeeze - easy!