How to undo car battery water cap?

I bought this century battery (model NS60LS) a while back, I'd like to check it's water levels and fill up if need be.
 
But how do I undo the caps?
 
Here's a pic ref of my battery. These are not the traditional unscrew-able water caps I was expecting.

 
 

A coin works very well, 10 or 20c

Senor_2
You'll just need a big enough flat screwdriver or similar and line it up across the gap along the straight edges

5SGTE
A coin works very well, 10 or 20c

rileseffect
set of needle nose pliers open them just wide enough to fit and unscrew

Ohh I see, man I was scratching my head on why they designed the caps that way. I guess to prevent rounding of the head?
 
Any ways I used the coin trick, worked a treat! water levels are fine.
 
Thanks guys!