M1 filter? Save your money and buy another brand. Everyone dogs the Frams because of the cardboard endcaps and the bypass valve. OK maybe the B.V. isn't as good as others, but there's nothing wrong with the endcaps, there only there to hold the potting material until the media is plunged in. Besides the filter media on most every filter is a paper base.
Anyway the Fram's have good filtration, especially the Tough Guard. I personally buy the Pure One. They have very good filteration as well. I buy the Pure 1's for filtration and becuse I can get them at Meijer during the family grocery shoping, Meijer doesn't carry any other brand.
See the attached chart, these aren't just my opinions, there based on data collected from an actual filtration test.
The whole thing wouldn't fit so I had to trim the comments and formulas.