Not expert on Laser cartridge replacement or refill, but from what I have read, you can get spotty results. Which is why checking your vendor out is important----its good to have a toll free number
and failing that make sure they respond promptly to emails. The nifty stuff forums does have a forum section on lasers-----but checking out the vendor is #1 in my book-----if they can't explain their return policy-----or be willing to answer your questions----its probably not worth dealing with them.
But have heard many good things about swiftink---be up to you to see if they are cost competitive in the Laser area.