Fitting TRVs to rads standard depth

[dynomikered]

Hi can some one please tell me if i can fit 15mm TRVs in place of normal rad valves i.e will the trvs fit directly on to the pipe work(15mm) without having to cut the olive of and add new pipework
I guess what i am trying to say is is it a standerd depth to the valve or are they all different and if so how easy is it
Thanks in advance
Mike

 

[twgas]

some are a straight change where even the tails in the rads dont need changing, some however need olives cutting off or even pipes altering a bit, depends on makes of valves.