Door frame depth for 3x2 studs?

[intogames20]

Hi,

My studwork has been built with 3x2" timber. I'm now going to have a go at putting in the door frames. I'm told I can buy a door frame kit, but I dont know what depth to buy?
On either side of the studwork there will be 12.5mm plasterboard and skim to go on, so I guess I need a depth equal to all this combined so that the architrave goes on flat and not at an angle? Thats about 103mm

Does this sound right? I'm not sure what sizes door frame kits come it?

 

[gregers]

iirc the 1 you want is 4 1/4 inch door lining,they also do 1 at 5 1/4 when using 4x2 studs.