Definitely the LAST time! I bought a nice slide and a backup slide for my bong, both I was told were 9mm. The backup slid in, but the nice one wouldn't, and just barely trying it at a different angle broke the female piece...I held them both up together and the nice slide was clearly bigger. I called but the very unpleasant lady told me that they're both 9mm, sales are final, I can't bring the pieces back in the store to show her...I'm out the $35 for the nice slide, and now I also have to buy a female piece that looks like a pain in the ass to replace. If all sales are final make sure you have someone that knows what the hell they're selling.