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I bought a new caliper for my mountain bike and notices that despite the pads looking identical they are not. So my Deore pads don't fit in an M445 caliper. Annoying, but not the end of the world.
I looked more carefully when I needed new disc pads for the road bike. I've got R805 brakes. Most of usual cheap sites don't stock pads for this brake. They do stock them for the R785 but as I checked part codes this time and the pads are different I'm a little wary.
Back in the day, you just looked at the pads and if the shape was the same they worked. Now it seems shimano produce a whole series of brake pads that superficially look the same but have slightly different dimensions so might not fit in your caliper.
I couldn't see anything with specific dimensions on the shimano site so you have to rely on what they say is compatible. This would be realtively easy but some places like uberbike don't have the full list. It looks like THe M515 pads would fit in the R805 brakes but I'm not all that sure.
https://www.uberbikecomponents.com/view-product/uberbike-shimano-deore-m515-sintered-disc-brake-pads
https://www.evanscycles.com/shimano-k02s-steel-backed-resin-disc-brake-pads-EV294350