I have not had to contact Surefire about anything because ive had zero problems with them.
As an international customer i have read on CPF that if i call them "in the middle of the night because of timezones" every problem will be solved ��
Bit off topic but i had an XL 100 and it had pwm even on full power so i couldnt use it at work because it gave me a headache watching lathechucks turning and coolant blasting.
Otherwise its a good light :)
brand:Surefire
model:6P
lumen:200 something
mode:one
runtime: few hours
other features:bored for 18650,mclicky switch with hardpress boot,Malkoff M60 drop-in
I believe you will get full lumens with a 17650 at least i haven´t noticed any difference.
And yes most of them fit but there can be some batteries that will be very tight.