// Definition
A specific mesh screen size (90 micrometers) used in bubble bag filtration, widely considered the sweet spot for capturing the highest quality trichome heads in ice water extraction. The 90u fraction often produces the most desirable full melt hash.
// From the Episode
Bubbleman specifically discusses scraping the 90u bag from the Colorado wash. The 90 micron is consistently referenced as the premium grade across Hash Church episodes.