http://www.crelant.com/accessory/crelant-new-collimator-head-s86ch-229.html
I post this link FYI, not for other purpose, just for those who carry Crelant flashlights, you could have a look to see if any of your lights could fit this collimator head. 
Do the holes in the head of these style light serve a purpose?
They help you see if the flashlight is ON when standing on flat surface head down…
Probably to see if the light is on when bezel down would be my guess??
Ostensibly it's to let you see the light when it's on, and facing down, to help with heat, and to provide a bit of added close up lighting.
From real world use: It's to make that nice plastic dust cover 100% useless, and reduce how well the light is sealed from moisture.
I just hope they did a testing prior to mass producing it and made that focus point right this time 