I'm upgrading to a K1100RS front suspension using 4 pot Brembo brake callipers. Purchased a pair of used 4 pot callipers in good order which needed new pads. Purchased a set of Cycleto brand [Chinese] 407 pads made by the Huan Tu E-commerce Co. Ltd. Problem:- The metal plates the pad material is bonded to have a manufacturing fault. The hole in the metal plate for the slide pin is incorrectly located. To get the pads to smoothly slide on the slide pin I had to enlarge the slide hole by using a round "rat tail" file. They now fit properly and are able to slide as is required. 
Yes I know... beware of cheap pads.

Be aware that the friction material probably isn't up to snuff either. The bonding could also be below par. I've had the friction pad depart the backplate on the rear brake during a turn; pretty horrifying. Suddenly no pressure in the brake, a locked rear wheel and the back end of the bike is sliding sideways across the junction. In that case the pad was a Brembo and in its defense, I had no idea how old it was.

Basically... even though you have paid for them, I'd still show them to the bin. One fault is enough to set up red flags about hidden faults.

I scour the web (mainly eBay) for someone selling close-out, damaged box, or just less-than-retail-price EBC, when I need brake em pads. I've been using them (and Dunlopad) for yonks and have never had a failure. They wear evenly, stop well, don't dust, and if you're particular you can get 'em in non-sintered, sintered and a flash red backing plate that's somewhere in between. I can find a single set for roughly US$20 quite often and keep extras in a shoebox for my various bikes. 

EBC FA407, FA407HH sintered, for early K four piston callipers. EBC FA18, FA18HH sintered & FA18V red, for K two piston callipers. Some K75 list FA171 in the rear but it is so close to FA18 that I don't bother sourcing it.

The last Chinese set I used lasted five minutes and dusted the disc, callipers and wheel all to hell. Binned 'em. Opinions may vary.

The only non EBC/Brembo brake pads I buy are Goldfren and then pretty much strictly for use in the rear caliper. I have used them in the front and they don't seem to be too bad, but old safety habits die hard (or preferably not at all!). I've used both the S3 and AD series and to be honest, couldn't tell the difference between them.

Ah.... right. I got curious and looked them up. I think I'll put them firmly on the trusted list. It seems that Goldfren not only make motorcycle brakes (including for racers), they make aircraft brakes too and if they can stop aircraft, they can stop my bike. They're made in the Czech Republic and the Czechs know a bit about building racing machinery. They're also a bit cheaper than EBC/Brembo/etc..

Thanks for the input. I'm binning the dodgy Chinese pads. Have purchased new SBS 644HS pads (SBS are a quality Danish company. They are a big supplier of aftermarket pads and were recently purchased by Brembo).

I have a spare SBS set x 2 for my K1300GT (Brembo cals) as well. Around the market since 1964, they're good stuff, and WebBikeWorld from Japan claim they're the biggest brake pad retailers in the world. I used to stock and sell them. I was only recently looking on eBay and saw sets for my K1200R (Tokico cals) at US$17.97 each. I might have to get a coupla them as that's a good price.

eBay SBS

Didn't they raise their price a bit minutes after I started to watch the ad?! Now $18.30 but still fair. I see that they're from $30 to $45 per set on eBay otherwise...

Edit: Just now dropped to $14.95 per set - I'm on it! I just grabbed four sets of brake pads for under $70.00 all up.