OVERVIEW 
Radium Engineering offers two different catch can kits for the R35:
*The 20-0565 PCV line kit mounts near the brake master cylinder in the back of the engine bay and interfaces with the hose that goes from the PCV valve on the engine to the intake manifold (vacuum).
*The 20-0555 crankcase vent kit mounts on the front of the engine and interfaces with the breather lines coming off of the heads and going to the turbo intake piping. This kit contains two catch cans (one for each head breather).
These two kits can be purchased separately or together. 
When deciding which kit (or kits) to purchase, it is important to remember that both kits working together offer the most protection from oil ingestion into the engine. The PCV side kit is effective at keeping oil out of the intake manifold when the PCV valve is open, such as during light cruising, idle, etc.  When in boost, the PCV valve closes and all the engine blow-by comes out of the head breathers. This is a good reason to have catch cans on the crankcase breathers

20-0555 DUAL CATCH CAN KIT, CCV, NISSAN R35 GT-R
To retain factory functionality, the two CCV catch cans run inline between each crankcase vent (CCV) port and the corresponding turbo inlets. 

At low loads, these catch cans experience atmospheric pressure. However, when the engine is at high load (WOT), these vents will experience high flow out of the crankcase. This would normally lead to oil and sludge accumulation in the air filter intake pipe. Oil accumulation will occur in the intercooler which lowers the thermal efficiency properties of the heat exchanger and leads to decreased performance.

NOTES: 
1. The dual CCV catch can kit does NOT address blow-by from the PCV valve side of the crankcase.
2. The dual CCV catch can kit is compatible and recommended to be used with the PCV catch can kit. See 20-0566-FL