Well you can easily measure the required length with a piece of fine wire of thick thread instead of relying on some Goodge info ordering the wrong size and ending up measuring it anyway and reordering

Don't rely on other people - you are the only one who'd do the best job of measuring them!
There are not too many mechanisms so posting a picture would help. If it's the same as RQ-4050FD, look for my thread it have all sizes posted.