Shimano Chain CN-HG40 6/7/8 Speed

If you have a genuine shimano chain pin tool, you should be fine. If not, either buy one, or find yourself a shimano quicklink for this chain to have ready for when you break the pin they give you halfway into the new chain. Finding a shimano quicklink for an HG40 chain relies on the goodwill of your local bike mechanic, since they only come with the workshop packs of new chain. KMC and SRAM powerlinks will fit, but be advised that the SRAM is a few tenths of a millimetre wider, so if your derailleur has annoyingly fine tolerances it could theoretically scuff on some gear combinations.

The other thing to prepare for is that this new chain measures half worn from new using a standard aftermarket chain measuring tool. So either use a ruler and measure the pins, or buy a genuine shimano chain measuring ruler. Prepare yourself for how expensive they are!

Another point is that this chain could be noisy on your drivechain for the first 100km or so. My cassette and chainring is 3 months old, hardly worn, derailleurs set perfectly (all shimano), and there was background clickity noise for some time before fading out. This could be because I cleaned the chain of it's packing gum and then lubed it before installing. If you leave the packing gum on you might not hear the clicks before the chain finally wears to your drivetrain arrangement.

It might be necessary to install this chain with the writing on the plates facing out, but no one really knows. The unofficial rule of shimano gear seems to be "If in doubt, pretty side facing out". The "instructions" that come with the chain are not instructive, and the online service guide which you should 100% read, is also only reluctantly informative. I mention all this because I've not had this problem before using SRAM or other inexpensive chains, and if you think something isn't right, it might not be you.