Can the Pro Magnum Shear I-20 #920 Handle Shingles?

All the magnum shear lines work on shingles, and the blades hold up well if you're just cutting shingles... Shingles don't need an especially sharp blade so it doesn't matter that the blade gets a bit dull. If you switch to cutting something else (for instance, fiber cement siding) the now blunt edge makes cutting difficult. This can be easily remedied by using one blade for shingles and another for everything else.

I've seen guy's cut aluminum flashing with an I-13, but the EZ-13 would probably have a hard time. The I-20 could probably do it too. Aluminum isn't an approved material to cut, so it probably voids any warranty on the blade.