I'd go with the Kool-Stop BMX pads and toss out the cartridge holders, in my opinion. Contrary to their name, they're not just for BMX bikes, working very well for any bike with decent fork clearance. They're threaded, easily adjustable, and they're flexible so they tend to give excellent stopping power without squeal and without having to fuss with them. I've had them on my road bike for a few thousand miles. They never squeal, and I haven't adjusted them even once since installing them.

Those are the ones that are recommended as primo from Sheldon's site. I've been looking at the CR720's for another bike, and fully intend to get another set of the BMX pads
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The ONLY caveat - the BMX are thicker than some pads like the Thinline, which is why I assume others recommend the thinline. However, I think the BMX is better, and I have to imagine any bike that has canti brakes should have the fork clearance for thicker pads. Heck, I've got them on my road bike.