You are buying one 5/8"  drill bit specifically designed for drilling of plastics.

1/2" shank

These drill bits have a zero-degree rake, a 60- degree point, and parabolic

cutting flutes to drill through Plexiglas, and acrylic plastics without binding

or " breaking out ". Very low torque and kickback means that you can

confidently use it with a hand drill without any fear of the drill binding

or wandering.Perfect for the use with Acrylic,Lexan, Polycarbonate,

and other plastics.