If it's for Acrylic get a 2 flute cutter, they will be called end mills or slot drills.
2 flute is better as with soft materials you need as much room as possible to get rid of the chips as they are usually cut faster than harder ones.

Acrylic tends to melt if run too fast in speed and feed, coolant is ideal or at least a strong air blast to stop it melting.

HSS is better than carbide as you can get a sharper edge on HSS

In a worse case scenario it melts and then re welds itself back again behind the cutter