3x Stronger, Thermal Shock Resistant, Absolute Safety. IMG Fully Tempered Glassware is heat treated to over 600°C and is rapidly cooled by cold air ventilation. This tempering process increases its strength and changes its composition for a more durable and thermal shock resistant glassware, which is less prone to breaking from sudden or extreme change in temperature. Tempered glass when broken, disintegrates into small chunks instead of sharp jagged shards, and is much less likely to do harm.