The cartridge for holding the filter piece simply does not fit the silicone piece of my existing Gill mask. The cartridge obviously is 'taller' than the slot into which it should fit. For this reason I have not been able use the kit to 'upgrade' my existing Gill mask. What a disappointment. I think I would have another go at it before I give up.
TERRIBLE - they take your $$$ don't ship and don't respond
My order has been sitting on a desk somewhere for weeks, they sent me a USPS tracking number that shows they generated a label but didn't ship for WEEKS
It works well and worth the upgrade.
Upgrade was fairly easy
I bought the upgrade kit to replace somewhat loose plastic latch of the non-Pro version. Upgrade was fairly easy and the kit fit well. My only gripe is that the filter is fairly expensive for P95 (at 55 cents per replacement compared to 70 cents per N95 equivalent Korean full masks), and you can't use any other brands of filter. Shipping overseas was like paying additional 40 dollars. Not a viable option. I am shelving the now-converted pro mask.
Pro upgrade worth it.
I wear my gill mask for about 8 hours a day, with a frew breaks outside. The pro filter upgrade is night and day. It also fits properly easier. Do not hesitate to go for the upgrade if you like the original.