I drilled out my PCKT One to take CCell cartridges. I got a PCKT One as a gift. Went to my local dispensary and got a Select-brand cartridge. The Select is a CCell, and it did not fit into the PCKT. Because the PCKT seems to be heavy aluminum, I took a chance that I could remove some wall thickness and not destroy the unit. My original hole was 10.48mm, and I used a 27/64 inch drill bit to open it to 10.68mm. The CCell drops right in with some clearance. This is probably not recommended, but it worked for me. If you try this, carefully measure the depth of the PCKT hole and wrap tape around your drill bit so you stop before it hits the vapor nozzle, be sure to clean out all the scraps of aluminum.