ThingMagic M5e - Manual (Page 21)

Heatsink
20 Appendix A: Accessory Specifications
Heatsink
Compatibility
Supports M5e and M5e-EU Modules
Dimensions
82 mm L x 54 mm W x 10 mm H
Mounting
M5e module is mounted to the heatsink using off-the-shelf M3 hardware (not included).
Heatsink can be mounted to chassis via M3 screws or M3 threaded mounting posts & nut.
Thermal pads are included.