My fairies are 1-6 inches tall, however, the 4-6 inch tall fae serve as hunters of their favorite prey- humans.
They fly at around 60 MPH, however they can only fly for 5 minutes. They can also hover, fly backwards, etc. Think of them like hummingbirds when it comes to flight.
They, because of their size, are amazing at hiding.
Because of square cube law, they are stronger than they look. They use swords about three times their length, and they stab people with them through the eye to kill them. Can't reach the eyes? Even better. Then, they'll dip the blade in poison, stab them, and wait for them to die (or not).
They have the intelligence of a human, and they commonly tag along with wolf packs like ravens do.
Humans only have medival technology.
By the way, I still want fairies to be extremely deadly, I just don't want them to kill all of my humans.
If you need any more details, just say so in the comments.