How to buy disc brake pads that suitable for my mechanical disc brake system for replacement

[ebikebeginner]

HI, everyone, how to buy disc brake pads that suitable for my mechanical disc brake system for replacement. I see there a lot type to choose from, which I believe for different systems. Please kindly advise. Thanks, you.

 

[sjpt]

If you post the make and model of the brake system we will more easily be able to help. Failing that a fairly close up photo.

 

[Andy-Mat]

If you post the make and model of the brake system we will more easily be able to help. Failing that a fairly close up photo.

....and some pictures, maybe with a ruler laid close to them...
Andy