Disclaimer: this strap was loaned to me to test out since I own/owned a Tissot PRX. This is in no way sponsored by Delugs or any other entity.

The aggressive curve down of the strap at the end links means that smaller wrists can finally enjoy the 40mm Tissot PRX. The bracelet tends to exaggerate the case size because of the fixed end links.
The quality of the rubber material is very good, unlike the cheap TROPICal style straps you might find with the same pattern/aesthetic. Rubber straps are nearly impossible to judge from photographs, but I can promise you there is a very wide spectrum of quality.
The end link fitment on the strap is excellent, and the design transition is fantastic as well. To match a somewhat dressy watch with the TROPICal style print is challenging, and I think this one was well executed.
The straps have a twin knob quick release system similar to the bracelet. Ken (Delugs) informed me that these knobs will be made larger on the final production units, but this setup was identical to the bracelet, so it can only get better from here.
The undersides are reasonably well vented with deep ridges.
The blue dial on the PRX Bucherer L.E matches the blue rubber strap almost perfectly. Unfortunately this prototype strap was only available in the smallest size (105/65) at the time, which is why my wrist looks like it is asphyxiating.
I hope this is a first of many more designs and colors to come. Delugs seems to have put a lot of effort and R&D into making this strap. And given the cult following of the Tissot PRX, I think this was a smart move.

To quickly sum up my thoughts – this strap is a blessing for those with smaller wrists that want to own a PRX 40mm. It wears a lot more compact, and feels comfortable while doing so. The quality is excellent and the design is well considered. A $200 strap for a $600-700 watch sounds like a very difficult ask, but given the following that the PRX has amassed over the last few years, I think there are enough die-hard PRX fans out there to make it work. A good rubber strap goes a long way in changing the experience of a watch, so this is worth saving up for if you’ve got a PRX in your forever-collection and you want to make it more sporty and more comfortable.

Strap: https://delugs.com/collections/tissot-prx/products/navy-tissot-prx-rubber-strap