Are glass dishes usable for both dairy and meat meals?
Glass dishes which hold actual dairy and meat foods should not be used for dairy and meat. Sefardim are generally lenient in this regard. For glass which does not hold actual dairy or meat, such as glasses for drinking, there is more room for leniency and many use them for both meat and dairy.
See Shulchan Aruch, Orach Chaim 451:26; Mishnah Berurah 156; Yad Yehudah 69:117; and see also Hilchesa Mibei Dina, Pesach, Nissan 5766, pp. 198ff.