Noone knows LOL,some does work,some doesn´t even though they look the same or at least very very simmilar.So it´s definately not only about desing,but also about material and pad compatibility etc...
push the pistons back in,put something like a piece of wood or wrench basically something that fits between them to hold them in place(there special block for this,but I doubt you have one).then just follow this
"Please note this auction is for cash on collection only. Can meet with the winner 30m radius of Reading(on weekdays) and localy around Harrow Middlesex (on weekends)."
Guess who is lazy?