I saw the picture of the prototype before seeing the vid (vid came at a later time). From just the picture, it appeared you were going with an eyeglass case (clamshell) design, but the vid shows otherwise.
If you're going with the "cigar tube" motif, then how about a modular design. By that I mean the case has different tubes sections that you can swap out to meet your needs.
For example, the primary tube would hold only one complete unit, but the tube has a female dovetail groove along its length. If the user just wants to carry a single unit, they can slide a pocket/belt clip attachment (with a male dovetail) into the groove.
A second attachment for the primary tube could be for carrying cartridges or 3ml bottles of liquid. This attachment consists of two narrow tubes that would look like the number eight from a bird's eye view.
This second attachment has a male dovetail for connecting with the primary tube and a female dovetail on the opposite side for an additional attachment.
A third attachment tube would hold an additional battery and a larger bottle of liquid (15/20ml?). This third attachment would appear identical to the primary (one long cigar tube), have a male dovetail, and can attach directly to the primary tube or the secondary attachment.
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By making it modular, the user can decide what he needs in a given situation. He might want just a single tube for one unit. He may want just the unit and a spare battery/15ml juice. The choice is open rather than fixed.
Here are some combinations with this design:
O = Primary tube (One complete unit)
: = Belt/Pocket clip
8 = Secondary attachment (2 small long tubes for 4 or more carts/3ml juice bottles)
D = Third attachment (extra batt on bottom/15ml juice on top)
{symbols represent a top / down view}
Just carrying one unit - O
- One complete unit only
Primary with pocket/belt clip - O:
- One complete unit only with pocket/belt clip
Primary with secondary cart/3ml attachment - O8
- One complete unit with several cartridges and/or 3ml bottles
Primary with 2 secondary cart/3ml attachments - O88
- One complete unit, even more cartridges and/or 3ml bottles
Primary with third attachment: OD
- One complete unit, 1 spare battery, 1 15ml bottle
Primary with secondary and third attachment: O8D
- One complete unit, several cartridges and/or 3ml bottles, 1 spare battery, 1 15ml bottle
Primary with secondary and 2 third attachments: O8DD
- One complete unit, several cartridges and/or 3ml bottles, 2 spare battery, 2 15ml bottles
Etc..
Note: I was going to open a graphic program to create better illustrations than the ASCII examples (above), but it isn't worth the time if it isn't even going to be considered. If considered, I can provide clearer visuals.
Thoughts?
EDIT: Forgot to add one more suggestion...
For the ring clip (button protector), if you're going to make a ring clip, it should also function like a pen/pocket clip. Have it 'snap on' like the current prototype, but include a clip into the design so it can clip onto your shirt/pant pocket for added functionality. Protects the button and aids in transporting the unit.
