Hansho Composites' special comprehensive report on Theory, Testing, and Manufacturing of Polar Bosses for Type 4 Composite Pressure Vessels Keys to success for LPG, CNG, Hydrogen, and other gases Metal neck polar bosses are the critical component for successful Type 4 composite pressure vessels.This new report reveals secret keys for success. Metal neck polar boss end fittings look simple and yet are often very difficult and frustrating. Polar bosses must provide high streng