These Ender3 style standard heater blocks without thru bolt holes to heat sink, purchased to test custom Cr E3 DD hot end extruder for better thermal mass for improved filament flow. To be determined.

Replaced a previous one with this and it is working fabulously.

This heater block I swear much better than the original one that came with my Anet A8. This one is lighter, heats up faster, fits the thermistor and heater block much better, and just gives better quality prints. It is also cheaper than many heater blocks you may buy directly from the printer manufacturer.