The plastic coating on a Shat-R-Shield HID lamp is guaranteed not to yellow and will withstand bulb wall temperatures up to 500F. Except under the foregoing conditions, due to variable conditions and fixture design, Shat-R-Shield does not warrant or otherwise guarantee the plastic coating on HID lamps for the rated-life of the lamp. The purpose of the coating is to contain virtually all glass fragments, phosphors and mercury in the event the lamp is accidentally broken. Shat-R-Shield suggests the shatterproof HID lamps be inspected and replaced if the coating material is compromissed due to temperature extremes.