Double wall 18/8 stainless steel thermal tumbler with copper vacuum insulation and push-on lid with thumb tab.
Superior insulation! The copper plating on the inner wall is an extra line of defense against temperature transfer. Heat escapes much slower so your coffee stays hot even in a snow storm, and heat enters much slower so your ice water doesn’t melt even under a blistering summer sun. On average, copper vacuum insulation can make a difference of up to 5C (9F) over the course of 24 hours.