I never buy a rechargeable cell without first consulting
http://lygte-info.dk/info/batteryIndex.html, developed and updated by cpf member hkj at tremendous effort.
For example, that particular "EagleTac" "3600 mAh" cell isn't tested for that list; but, there is an EagleTac "3100mAh" and "3400 mAH" cell on that list. When used in ZL's, I usually compare at the mWh rating at 3A down to 3.4 V (that's a conservative, useful capacity for me, using it outdoors at pretty high brightness on my bike--actual current is usu. below 3A). The "3100" and "3400" EagleTac cells were tested to have 4.1 and 5.0 Wh, respectively; the NCR18650GA (rated as "3500mAh") was tested at 8.0 Wh. FWIW, I exclusively use the NCR18650GA's that ZL sells on their website in my ZL's.