What is this stuff called?

[truckin 79]

It is kind of tacky but is used as insulation for the copper pipes on this evaporator. I need to find some more of this stuff to seal it back up again. I am just about ready to flush and put new hoses on this unit. Also anyone know what the probe is used for that goes into the fins? You can see in first picture the probe and then the crusty round circle that it went into. The wires are connected to a little black box,so not sure if it is just another safety switch not sure.