1/4 x 3/8 inch vinyl air pipe (per metre).
Best to use a plumbing cleaner then pipe cement to assemble. Be sure you do not glue over the air hole of your manifold as it is easy to web the glue when using on a small area.
Often also used for the Ozone venturi. Fits in side 3/8 Inch Air Pipe.
SOLD BY THE METRE COMES IN 180M REELS