Shortly after I jumped into CNC machining I ordered some single flute mills from Aliexpress (the 5mm one on the left ). I’m still happy with the quality of the cuts I can get with them.
Some weeks ago I ordered the two roughing mills on the right (6 and 4mm with three flutes). I started with 6mm bit  and got nice results and less noise during the cutting process. It struggles a bit while diving straight into the wood (ramp plunge would definitely help).
Today I took the 4mm one . I was impressed how easy it cut through the material and diving did not seem to be a problem.
- Material: Birch plywood 15mm
- Mill: dia 4mm; 3 flutes
- Spindle Speed 12000 RPM
- Pass depth: 4mm (4 cycles to cut trough the sheet)
 5 stücke Schaft 5mm Hohe Qualität Hartmetall CNC Fräser Eine Einzelne Flöte Schaftfräser Werkzeug 5*25mm|mill tools|single flutecnc router bits - AliExpress
[2 & 3] WeiTol freies verschiffen TCT drei flöten gerade bit 6mm ende mühle holz schneiden werkzeuge gerade router bits für feste holz|bits 6mm|straight router bitstraight bit - AliExpress