At your suggestion I checked out Premium Guard Extended Life. The one thing holding me back was the bad efficiency specs posted on their web site. So I started looking at MicroGuard Select Extended Life, also made by PG, and cut apart samples of the PG4476EX and the MSL10322. They are both very nice and almost identical, but I noticed some subtle differences. One is place of origin: the PG was made in China, the MG in Vietnam.
Another difference is the filter media. The PG media seems to have a finer "grain", it's "smoother". The can is also a bit taller than the MG, so a bit more filtering surface area. The media thickness for PG .0360", for the MG it's .0363. This is measuring ten plies then dividing by ten
The gasket is also different, the MG has a rounded top, almost like an "O" ring. The PG is flat, both are red in color.
But then I saw your post about the web site being wrong after you contacted the company! I'll repeat your info here:
It makes intuitive sense that the finer-looking filter media would filter smaller particles, so that in conjunction with your efficiency report now has me on the PG side of the fence. They are both very clean, without any spattered glue like the Puro One, the pleats were straight, the ends crimped with a metal clamp, and the bypass valve was coil-spring backed and built into the bottom of the filter element, so no permanent bypass leaks! Both brands also came with a cellophane seal on the can, which suggests quality and an attention to detail not seen in many other brands, at least in my mind.
Bottom line: I'm going with the Premium Guard Extended Life.
I'll attach some photos showing the filtering media. The first shows the texture difference, PG on the right. The second shows how they look with a light behind, PG on the right. The third photo shows the gasket difference, this time PG is on the left.
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