It's common for a rebuild kit from Walbro, or most any other carb company to fit more than one carb.
It's also common, especially lately for a kit to have more than one type of diaphram in it.
I recently bought a kit that had both the neoprene(black) pump diaphram, as well as the acetate(blue) pump diaphram in it.

Per the attached picture, it seems that the blue film diaphram isn't a very good pumper.
What bothers me a little is the fact that some kits are not adding the black parts in the kits anymore.

Question is ---> Does anyone have experience using the blue pump diaphram, or blue surge diaphram in an aircraft application?
I am also trying to find out exactly what a surge diaphram really does?
The Walbro WT series manual shows one in the exploded view, but my Wt-201B didn't have one when it came apart from the factory.

Thanks
Bob