If they're genuine, I liken it to buying from batches that didn't pass QC, that someone ran out the back door with and is selling. If they're knock-offs, there's always something not to spec, different, cheaper materials used to cut cost. It's a crap-shoot, you might get good ones, most likely not, and as far as warranty, the best you can hope for is a replacement of the same thing you bought with another one (if you're lucky). Only tried them once, wasn't my choice, a purchasing agent for the company I was with at the time decided to try to save a buck when we did an overhaul on one of our Rolands... They looked the same, but never fired as good, dripped and clogged constantly, random over spray issues that would come and go, and completely failed within about a year. After all the wasted time and material, plus the expense of having to replace them all again so soon with OEM's, not worth it in my experience.