Bio Size - The device with cartridge attached is about an inch longer than an iPhone. With the cartridge detached it breaks down into two pieces smaller than a cigarette. It fits comfortably in a pants pocket. Durable – The OPen is made from metal. The cartridges have plastic but they are disposable so it’s expected. The cartridge and device have a threaded metal connection. Stylish and Sleek – It looks cool and has a small profile. When I take it out in public people either don’t notice or when they do think find it intriguing and mysterious. Battery Life - Even with daily use I can go 3 to 4 weeks without having to recharge my pen. This blew me away and is one of the most impressive parts of the pen. Cartridges - Cartridges are easy to change, strain specific, and come in Sativa, Indica or Hybrid. Even Buzz - The oil provides a consistent and even buzz.