They are only available for newer carb models. You can’t find compatibility with any ol Walbro carb from the past 20 years, even though it’d be trivial for Walbro to do.
They have a thin membrane that is very fuel, and especially alcohol, resistant. What makes it good is how well it resists hardening over time.
Unfortunately it’s properties also mean it has no structure, unlike a rubber diaphragm with a built-in contour shape; it’s basically like Saran Wrap. And it’s very difficult to bond anything to it. So walbro is using a metal spring to actuate the gasket as a pump.
But, it’s also incredibly delicate, easy to tear and so it requires a special installation sleeve to install. It isn’t hard to do, but it’s requires paying a little more attention. It also costs about twice what the OEM gasket kit costs, or 4-10X what an aftermarket gasket set would cost.
But, for a consumer that maybe only uses OPE a few times a year with regular ethanol pump gas, and then puts it away and 12 months later it won’t run because all the gaskets are gummed up and hard, this might be a nice solution to get better mileage out of service intervals.