The mechanic told me that I need to change the rotors for my brakes (which makes sense I guess, since the bike is 7 years old and has been used quite a lot). The bike is at 2016 giant reign, the brakes are Shimano Br-M615. The rear rotor says "Avid 180mm hs1", the front one is Shimano and is 203 mm wide. Both have six screws.
The mechanic charges me €30 for each rotor, which after a quick search seems like it's quite expensive. So my question is which specs do I have to watch out for when buying new rotors online. Also if you have any suggestions about where to buy them. I live in Europe and usual shop from bike discount. I found a few with the same diameter and number of screws, but the specific model for my brake is not listed as compatible.
Thank you

If the rotors are of good quality, that’s actually a pretty reasonable price — especially if the shop is doing the installation.

I agree that is a very reasonable charge. If you do decide to buy elsewhere all you really have to match is the rotor diameters and that six bolt mounting is a standard. The only other mounting method is "centerlock" and the difference is very obvious. Rotors come in a wide range of quality and price from plain stamped one-piece ones to composite rotors with an aluminum spider for heat dissipation. Pick your quality requirements and price point.

I will agree the price seems quite reasonable, especially if installation is included in the price. You could indeed find cheaper rotors, but you get what you pay for. Cheaper rotors are cheaper for a reason. Some won't dissipate heat as well. I am assuming they will be changing your pads as well, correct?

And then they'll warp, and you'll need new rotors again.

Or worse yet, they'll melt while descending a long downhill and then.........well........we don't want to go there. Brake fade is also a possibility if the fluid gets hot enough to boil.

I tried various discount rotors, they were all junk. If they worked halfway well, they didn't last. Most were loud, flimsy, pieces of junk that didn't work or last at all. Oh, and they're impossible to return, so it wad a real waste. I now take advice at the bike store about which ones would work well.

Thank you everyone for the answers. I'll check my options online and see what I can do.

info to consider while shopping.. and some rotors will not like some pads... do take time to read the articles or you will be needing more parts real soon

https://mbaction.com/2product-test-s...pad-compounds/

https://www.bikeradar.com/advice/buy...sc-brake-pads/

All good comments above and 30 Euro for part and install is reasonable; however, I agree with a couple of posts that the better quality rotor "generally" the fewer problems down the road, better longevity and better performance. The, "Buy once, cry once" comes in to play here...within reason. As far as availability on-line, do some homework and read some reviews, lot's of opinions out there...

Me personally? I have Shimano "Ice-Tech" rotors on my one bike with disc brakes. I love them but they aren't cheap depending on which ones you look at.

If it seems to you expensive then use v-brakes))

So like I say with any braking system good small parts are important. In this case pads and rotors would be the main thing (and potentially hydro hose but if you have good quality brakes as you do that is usually less of an issue than with cable stuff) Cheap rotors are never worth it unless in an absolute emergency and that is all they have. Get good rotors, it sounds like the shop has rotors at a decent price. Yes there is cheaper stuff there is almost always cheaper crap out there some of it legit some it fake but doesn't matter it is crap. My favored rotors for Shimano brakes or 1.8mm needing brakes would be the IceTech rotors from Shimano they work really well and are worth the price. It is in comparison to a new braking system a low cost item that can greatly improve braking that and some good pads (I like Kool Stop or SwissStop generally) If you are trying to just go cheap then avoid at the very least resin only rotors.

And the fact that my brakes (BR M615) are not listed as compatible shouldn't be a problem?

That is not the Shimano tech docs. However the rotors may not be listed as compatible if you are using resin pads, they are probably requiring resin pad only rotors but just use a good metallic or semi-metallic pad and use the RT-86.