Coir (shredded coconut husk fibers) - gallon
Coir is the long fibers of the coconut husk, and is excellent for a variety of orchid potting needs. Some people pot straight in the stuff, but most that I've seen use it in wooden slatted baskets to keep orchids like Vandas and Ascocendas upright!
It's coarse and stiff, so you can pack it loosely around roots or plant bases and it will offer stability without smothering. It is slightly moisture retentive, but not too much, so is great for roots you want to dry out quickly.
Multiple other uses as well!