Hello,
I can't quite make out if your T-lock shoe has an open or closed cam like the closed 15-195 or open 15-195B. We'll include images below to help you choose the correct match.
These T-lock shoes are used with the S795 channel balances. You'll need to remove yours from the window to locate the stamp code on the metal channel, which should correspond to one of our strength options. You'll also need to confirm if the pulley uses the same type of screw tab for installation. Thank you!
The only difference between the 15-195 and 15-195B is that the 15-195B has a hole in the back of the cam. That's what makes it an "open" cam shoe. You can see what I mean in the images above.
As for using alternative lengths, I'm afraid that won't work. These are very precise systems and any change in size will prevent the hardware from working properly. We always recommend replacing the old hardware with an identical replacement. I apologize for the inconvenience.