What size is your PDP Backstrap?
Our PDP full-size backstrap mimics the Walther "medium" backstrap.
Do Your Walther PDP Parts fit the PDP Pro?
The PDP Pro (as we understand it) is a PDP with cool accessories.
Assuming yours is a full-size gun (18-round flush-fit mags). Everything we make for the PDP full-size should fit. That said, I'd advise you to buy the whole set at once if you intend to use our magwell.
The basepads and the backstrap work as stand-alone products, but the hardware to attach the magwell is built into the backstrap (the magwell won't attach without it). Also, once you attach the magwell, you'll need extended basepads of some sort to get the mags to lock in properly.
Walther PDP Backstrap Cross-thread Issue
Walther PDP Backstrap Installation
PDP parts won’t fit my PDP magazine!
Sounds like you have a PDP-C (Compact) with the 15-round mags. If you do, you want parts for the PPQ/PDP-C magazine. Walther - PPQ - Page 1 - Taylorfreelance (taylorfreelancestore.com)
The PDP (full size) magazines are narrower, similar to a CZ or a Canik.
Looking at your order, you ordered a +0 for the Canik. That won't work on a PDP-C, and it won't work on the PDP full-size either -- the shoulders have to be milled off slightly to let the magazine go far enough up into the frame to lock in. (It's a common misconception that Canik mags and mag parts work on the PDP -- they ALMOST do, but not quite.)