The Pura #20 Quartz Sleeve is a compatible sleeve for use with Pura’s UV Addon-3, UV20 Series & UVBB Series systems. The Pura QS36003035 quartz sleeve provides thermal protection for the system’s UV lamp and protects it from possible damage. NOTE: It is recommended to clean and inspect the quartz sleeve when changing your filters, and each year when replacing your Pura QS36003035 UV Lamp. Replace your Pura #20 QS36003035 quartz sleeve if damaged or if it cannot be cleaned by non-abrasive methods.