Keep your fit in the big leagues with the New Era Mets 9FORTY A-Frame UPSD Arch Cap. Crafted from 100% polyester, this baseball cap provides a lightweight yet sturdy structure to keep you comfortable all season long. Stay in the fan zone and show the world who you stand with in the New Era Mets 9FORTY A-Frame UPSD Arch Cap. Part of the 9FORTY A-Frame Arched collection. 100% polyester.