It's quite simple actually. The first half or so of the charged set of LG HB6 batteries are more powerful for the,say, the 900mAH. Similar to the VTC4s or other Sony 18650s that used to reign supreme, which is too bad since VTC5s were known among vaporizer users to be more suitable for mech mods and custom coils, which often go hand in hand. No regulated box mod currently on the market, or any that have been on the US vaporizer market have had been able to recognize custom coils with resistances as dangerously high as .01 for example. Only particular (not ever dictated by expensive priced devices or certain brand) regulated box mods are usually only able to recognize .1ohms or .5ohms and that's a rare and random feature, or lack thereof, the computer chip which is basically a loaded up motherboard with tiny components if you understand custom Desktop builds...which I sell...so the RX200 which is created by Joytech ironically one of the least bang for your buck, not current with their ego tech even though their features are new creations-though features nobody wants as badly as say the Smoktech Stick One or Stick One Plus ego system for around 34 dollars or less depending on where it's bought. It's a .25ohm Kanthal, .3ohm Kanthal, .35ohm clapton VW mode flavor focused coil. However it has the Nano TFV4 subohm tank which is obviously tiny, needs it's own NANO Smoktech coils, has a built in 2000mAH or 2100mAH depending of the shape and size of the device and liquid capacity which differs a bit between the short Stick One I think 2 inches longer with a much thinner ego battery and fat Stick One Plus which has the hardly impressive 2100mAH ego battery charging with a simple USB to AC adapter for USB cord device connections. The old Aspire CF Suhohm on the roids my father took while I was an adolescent taking his closed fist irrational rages of violence like a champ. Some humor although it's true it must be something to joke about while thinking about the past. Anyway, .01 built coils which are usually something you'll see used strictly on unregulated mods (with wattages, voltages, and gosh willing-a VERY power pair of 30amp batteries. Mech mods run in parallel, or is it series, I forget. One of those ways a dual 18650 mech mod gains such power especially before LG flooded the market with a battery for every vaping application, was the fact mech mods would add the dual 30amp batteries and a fully charged cell's nominal voltage to create a 60amp min continuously discharging powerhouse to help burn their lungs at 200W with a .01ohm dual cotton Kanthal coil that the user made themselves. Regulated box mods run in the other (series or parallel and that's something we should all look up again to remember) battery style so not knowing too much about the science behind it, only voltage is increased to levels more than double a single battery regulated box mod would have available. Voltage is as important as mAH and even the amperage that's discharged even at 40% life remaining before the cells completely die. HB4s in a Wismec Reuleaux RX200"S" or any Reuleaux model including DNA versions, are almost 100% consistently putting out the tested and concluded fact of HB4 battery lasting longer like perhaps it's realistically a 1640mAH battery is used under a 120W constant vaping application. My Wismec triple 18650 has 2 out of 3 batteries combining max charge voltage levels and perhaps even temporary increase in amperage while doubling the mAH as those 2 batteries are set up like a mech mod in terms of the mAH of each of the 2 cells creating a 1500mAH HB4 triple battery reg. box mod that's already modest as a single cell so I believe the mAH become close to 3200mAH while the additional battery just further adds power (mainly voltage) and also allows for the updated RX200"S" firmware that increase the device's max wattage potential to 250W without a pulse feature in the given chipset. 3 LG HB4 batteries, two running together and double their mAH, as all 3 combine additional voltage and temporary amperage that is just completely uneeded but a part of the way these batteries function. An HB6 set of three in the same reg mod would be totaling approx 2880mAH and the voltage and increase temporary amperage would become muuuch weaker, less satisfying before the real enjoying vapor/flavor production had been working as it should or users would LOVE for it to had it been using a Subohm Tank with very high res. coils like using a TFV8 Cloud Beast, Uwell Crown, Mutation Indulgence, etc. Now the HB4 isn't SUPER powered for the few minutes of chain vaping to paint the picture for you or a while vaping a little bit at one time, also won't lose life for a couple hundred mAH longer while using more than enough volts, amps, and pushing up to 180W on a TFV8 coil that doesn't suggest that wattage but states that users have the option to safely vape like that without burning the coil which is only one of 4 available coils, all of which are .15ohms besides the one particular coil that is a .2ohm coil described as a "cooler and smoother vapor and flavor production turbo tank still able to handle a max of 140W though 100 is said by all who own one already to be more than enouogh wattage unless users want one hit so far bar-raising clouds (which are my favorite part about subohm tanks) produced at 115W. HB2s aren't much better than an LG HG2 in terms of performace and it's length of highest points of power. Sadly is drops off what little additional full charge power Volts/Amps/ complete high or any Wattage use freedom. So The tests are out from 2 different trusted battery experts not affiliated with the vaping stores, sites, boooming business, and definitely not influenced by profits or kickbacks. HB2s, HB4s, and HB6s all have identical specs according to LG's own official spec and cell data sheet. It takes millions of dollars to create new 18650s ESPECIALLY ones that are innovative and didn't follow anything similar that came before. HD2s are apparently better for a certain min 25amp 2100mAH 3.6 nominal voltage cell. Thrown 3 in my device and get 4200mAH total, however the closer to 20amp than 25amp cell HD2C is average but maintains average full charge power for longer than the HD2, however, HD2C batteries turn from almost 28 amps for 5 hits off the tank to a steady 20amp cont. discharge with slighty better voltage than LG HE4s or LG HE2s from years ago. I ordered 3 HD2 18650s for $16.50 tax free and very cheap shipping although slower due to my NYC residence and their-California-I'm almost sure that it's Cali...but anyway. I found a 25amp cell for TFV4 low wattage and slightly lower resistances than the 30amp cell I'm using now (in sets of 3 mind you) and will be saving with a married charge as great as possible. And that is why you're losing money. I'm not a retailer. I'm a consumer who uses and see what every consumer with similar vaping styles has been using, and I think you should at least order the LG HB4. The others under 30a aren't worth stocking. but HB4s!!!! the VTC4s killer, the no "drop-off" power cell for reg. box mods. If you read all of this Thanks. If you didn't you basically didn't get anything out of it and your question wasn't answered and I answered it from every angle I mean I gave all the reasons HB4s are in all of the reg box mods since it had shown up on sale in certain places online and very few good mom and pop shops which since I live near Queens, we have the local shops that rip you off on these vaporizer products but often don't bother wih taxing me. `