Pyrex clear glass insulator with smooth drip skirt. It is 4" high by 2 1/2" diameter at the base. It has the Pyrex name with "T.M.REG.US.PAT.OFF." under it. On the back is "Made in USA" under that is "Pat.Appd.for" and then it has "ED" It has a chip at the bottom of the dome as well as an internal crack at the dome edge and a chip inside at the treaded portion.