The Husqvarna 357/359 Vstack Adapter is epoxied to the stock intake elbow, a hole is then needed in your top cover to allow room for the air filter to stick up out of the saw.
This Vstack Adapter will fit any 2" I.D. air filter of your choice. I recommend the Red Beard Saws Air Filtration system, PK-82, or the Green Weenie foam filters.
I also recommend using JB Weld Plastic Bonder to bond this part to your stock intake elbow.