I run a 1/4 inch down spiral ball mill: Amana Tool 46476 Solid Carbide Double Flute Down-Cut Ball Nose Spiral 1/8 R x 1/4 D x 1 CH x 1/4 SHK x 2-1/2 Inch Long Router Bit https://www.amazon.com/dp/B0112THXPC..._fgdkAbX48R8RV
It's great for making radiused pockets