I redid most of my 18650's lately. I used to use regular heat shrink tubing, but with the re-do, I switched over to fasttech's pre-cut transparent wrapper for my 18650's. It works out much better for me then the thick heat shrink tubing.
The FastTech pre-cut are 72mm long and works very nicely when without a protection board. With the transparent wrap, I wrap it over the original battery wrap and I know I got good coverage and yet see the original battery markings/labels. I add my label (battery ID, date I salvaged it, and where from) under the transparent wrap. With the original wrap under the transparent new wrap, any scraps/wrinkles made during battery extraction causes the new wrapping to have a bump. This increases the battery diameter just a bit. It works very well.
72mm is a bit short when a protection board is added. If the wrapper is 74mm or even 75mm, they would be perfect. The protection board adds 1.5mm. The top-cover also adds another 0.5mm or so even while it is not a button top with a protruding nipple. Room to sneak the wire in (to connect to the protection board), insulation...
[topCover 0.5mm] & [insulation and wire to protection board 0.8mm to 1mm] & [battery 65mm] & [insulation+tape 0.5mm to 1mm] & [protection board 1.5mm]
Total= 68.3mm to 69mm
With redoing the wrapping this time, I am more experienced than the first time and I generally get it down to just around 70mm long. So, 72mm wrapper is too short to grip both ends well. I usually let the top loosely grip (saving more length for the bottom) and add another layer - this time grip bottom poorly saving more length on top to grip the top well. The two layers grip both bottom and top well and (double) protects the bare-wire (that goes from + to protection board) from external scrapping. This triple layer (original+two new layer) battery is not just long, it is also a bit on the fat side. The round wire from + to protection board adds 0.5mm to the diameter plus 0.1-0.2mm insulation paper under it. So my protected batteries (newly rewrap ones) are 69-70mm long, and 18.7-19.2mm diameter.
EDIT: updated - with more suitable material to make it shorter and thinner diameter 18.54-18.57mm and 69.25-69.70mm long
For the protected batteries, I decided to redo it one more time since the thick diameter is not fitting into my (new) second 18650 flashlight:
- use fasttech's NON-pre-cut transparent wrapper
- use copper foil instead of wires to connect B+ to protection board
The fasttech's NON-pre-cut transparent works well (cut to 75mm+-1mm) so one layer will do. With the copper foil (5mm wide 0.03mm thick) plus kapton tape under and over (total 0.15mm max). The copper foil is very difficult to handle but far superior to wire. It is not as thick as 26AWG wire even with kapton tape under and over it. I cut down on the diameter by at least 0.5mm.
With twelve 18650 redone, all diameter range 18.54-18.57mm and 69.25-69.70mm long. Now all twelve fits into my flashlights.