Septa BTO® is Bleed and Temperature Optimized for today's most demanding GC and GC/MS applications; it is the finest GC septum we have tested. Septa BTO® is formulated to extend low-bleed and outstanding mechanical properties of premium GC septa to the highest-temperature applications. It retains remarkable softness and pierceability at high temperatures, with extremely low bleed, and has been optimized to reduce injection port adhesion.