I've been vaping on my new oil pen for a little over a week now, and I have to say the one I bought is a quality device that seems to do everything it claims to do... so far, anyway. I went with the Double Agent pen by Gentleman's Vapes, and I use their mega v2 oil cartridge. You can pack up to a gram of oil/shatter/wax in there! It takes me a good 3 or 4 days of vaping (5 or 6 times a day, I would guess) before it's time to refill the cartridge. I haven't even packed a bowl or smoked any herb since I got this thing!