Can anyone using these tell me what size bolt i need to hold them in place?

I assume that they are"Gaz" ones from Dampertech.
I just received mine from them , the bolt holes are 12mm.
Are your front & rear units the same length?

yup same lenght, i just wasn't quite sure cos i measured the hole as 13mm, must've messed up somewhere along the line.

Are you sure it's not 1/2" ?

it could be, but would have thought that new parts would now be produced using metric measurements.

called the bloke at dampertech today, he was quite helpful, he said that it is indeed 1/2"