As of January 2019, Instech no longer sells 2, 3, 3.5, 5 and 7Fr silicone tubing for laboratory animal research.
While silicone is inert and flexible, it is highly permeable to air, which can lead to poor patency, and also does not make reliable friction fit connections. Instech continues to sell polyurethane tubing, the preferred material for intravascular use, in bulk spools and as finished, sterile catheters.
Instech also continues to sell 1/32in wall silicone tubing for peristaltic pumps and other external applications.