What are intumescent hinge pads for fire door hinges?

Intumescent (graphite type) hinge pads. Used on FD30 (30 minute) and FD60 (60 minute) timber fire doors. Don't fit your hinges without them! Available in a range of sizes, both radius and square corners. Made in the UK! Available in 0.8, 1.0 & 2.0mm thickness.