2008 1.6hdi injector removal, bolt size/tool?

[stu76]

hi.

does anyone know what size or what tool is used to remove injectors for a citroen berlingo 1.6 hdi 2008 please?
looks like a allan key but tried my sizes and are either too small or too big!
presume prob a imperial or metric size required?
2 bolts that hold the injectors inplace. allan key shape with a star at bottom

if anyone knows please drop me a reply asap as much appreciated.

thankyou.