The mounting holes are closer together, it makes it easier to fit in tight spaces, two of the tabs match the normal hole spacing. There is the option to use a clip-in base when the standard hole spacing is required.

The main differences are the new mPTX transponders have the latest electronics with contactless setup and are a smaller size, lighter weight, as with the PTX (NS) they have a replaceable lead and now also an easy replaceable case. We now have the mPTX Pro with a stealth 'pro' black lead to satisfy the serious racers

The PTX (NS) and the new mPTX / mPTX Pro are compatible with all systems.

Terry_S