Stackable glass espresso cup Φ6.2x6.8cm. Made of tempered glass. Glass that has undergone thermal hardening treatment which improves its mechanical strength, thermal resistance, and safe breakage properties. Tempered glass is 5 times stronger than ordinary glass, retains its characteristics at low and high temperatures, and withstands temperature gradients. In case of breakage, it shatters into small relatively harmless pieces instead of large and sharp ones to avoid injuries.