Extruder rebuild mishap

Ordered wrong heat break…
the top of old is about 4.85 mm dia.
the top of new is about 5.5mm and is shorter overall length and fewer threads into heat sink.

(Rebuilding the original Aerostruder .5mm that was in my early generation Mini2.)

What brake to order?

You would want to look for the e3d v6 heat break in 2.85mm.
Are you trying to convert it over to 1.75 filament?

If so, this would not be possible as you would need to replace the entire hot end.

Thanks! for your reply.