Zephyr is DH's clear glass that has been formulated to melt smoothly and easily in the torch; resist boiling and scumming; have a low reactivity with silver glasses; exhibit a low seed count and be fingerprint and dust free (NOTE: ONLY APPLIES IF ORDERED IN THE PRE-PACKED 1 LB BUNDLES THAT CAME FROM DH). Every pot of Zephyr is tested compatible with Effetre clear and other 104 coe glasses.