These are only required if the wall has been partly rendered or pebbledashed (called harled in Scotland) creating a step in the surface.
It is possible to bond several layers of packers on top of each other to build up thickness to the closest 5mm. For example if the render were 25mm thick you would buy one RP500 - 20 and one RP500 - 5.
TIP:
Some customers have also found the Render Packers useful when they have been bonding a Snorkel Vent to a very rough surface such as coarse pebbledash. The method is to trim 2 packers so they cover the back of the entire flange around the Snorkel Vent. These packers are first bonded to the wall using a fairly small bead of adhesive sealant. Then you can apply as much sealant as you like between the inside of the packer and the wall, as this will not be visible once the Snorkel Vent is bonded to the front of the packers.
