Okay, let's break it down.
If you want something exactly the size of a king-sized cigarette, then your only options are the Njoy King (disposable) and the Colibri Nano/Micro (rechargeable). The Colibri is a 90 mAh battery. this device is 7.2 mm in diameter.
The l88b, aka Blu, Volcano or Jet (in the States).These batteries are the same capacity as the Colibri, but they are 8.5 mm rather than 7.2 mm.
Somewhere in here falls the eRoll/eMini. The batteries are 90 mAh but I'm unsure of the diameter. This is the only proprietary device in this class.
Next comes the j108. Same diameter as the Blu et al, but when assembled these are the same size as a 100-sized cigarette. The older models are incompatible with other 510 equipment, unlike the Blu and others mentioned. The Sidesho by Modern Vapor is the only newer model j108 device I know of and is compatible with other 510 devices. These batteries are available in automatic and manual.
Next up is the Joye 306. 8.6 mm batteries, 180 mAh capacity. And yes, there is a pronounced difference between 8.5 and 8.6 mm. Many drippers love the 306 atomizer.
Next is the 510 and 808/901 devices. These are 9.2 mm or 9.4 mm, I forget which. 510 and 808/901 simply refer to thread type; 808 and 901 share the same thread type but are incompatible in automatics. The l88b, j108, 306 and 510 all share the same thread type and are fully compatible. These batteries are available in 180 and 280 mAh, in both auto and manual. Unlike the other sizes mentioned, there are a number of clearomizers available: the CE2, CE3 and the Nano.
Next is the M1/M3 by Kanger. Mainly available in 808 devices, but a 510 model is also available. The M1 is 480 mAh and the M3 is 380 mAh. There is one carto and one clearo designed to fit this battery seamlessly.
Up next is the eGo and the vGo. These are larger devices, usually between 14 and 16 mm. The eGo has an inner set of 510 compatible threads while the vGo has an inner set of 808/901 compatible threads. These are available as 650, 950, 1000, 1100, 1200 and 1300 mAh devices and sometimes with variable voltage. These are usually available only in manual mode, although some are also available in automatic. The Echo mentioned in my signature is an automatic 14 mm 808-threaded device, but it does not have the exterior threads of a typical eGo or vGo. If it helps, these are about the size of a cigar.
After the eGo comes a large number of mods. These devices can come in a wide variety of sizes an shapes. Only one is available as an automatic; the vast majority of these are manual only. The most important thing that separates these from other devices is the fact that they use replaceable batteries similar to other battery operated devices and are generally more cost effective in the long run compared to other models. I honestly don't know enough about the various devices to explain the differences between them.
Really, at this point it comes down to choosing a device and purchasing it. Will you waste a bit of money? Possibly. I know I have over the past 6 months. I also know I immediately went from 2 packs a day to roughly 2 packs a month and I seem to have finally kicked cigarettes for good. The $50.00 or so I wasted every month trying different things would have bought me enough cigarettes to last 2.5 days, so I don't lose any sleep over it. So pick a kit and try it out.
We'll still be here if you need help.
![S[A]E](/data/avatars/s/136/136117.jpg?1429716254){kind=avatar}
