This heater block is based on the E3D Volcano (Version 1) style. This means it uses a thermistor with a glass bead, and is retained by the M3 button head screw.
We round over edges of the heater block which can contact wires. We put the extra TLC into this part to ensure your wires stay protected. We do strongly recommend covering metal surfaces which can contact your wiring with Kapton (polyamid tape).