Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Incompatible with some phones

This product may work well for phones with which it is compatible; however, it is incompatible with our office phones and I believe it will be incompatible with a good number phones. The problem is that the plug is too short, as short as it possibly can be. The wide twisty part, which sits directly behind the plug, causes the problem...the shortness of the plug results in a plug that cannot be inserted deeply enough into some handsets for it to lock in place. Our office phones are the Cisco IP Phone 7945, and this device does not lock into place at all. It also doesn't lock into place on the back of the phone for exactly the same reason, making it useless for this phone. MOST of the other designs for competing products, if not all of them, have a longer plug, which gives them a fighting chance of being compatible with more phones. I do not recommend trying this product unless you verify that your handset only requires a shallow plug.