If you are doing a Polymer80 pistol build, they recommend using an end mill to remove the top tabs and/or cut out the barrel block they cast in the barrel channel of the frame.  They used to include end mills and I always wished they were a tad longer to help remove the barrel block.  I used nippers, files and sand paper to remove the top tabs but I did like using an end mill to slowly remove the barrel block.

Because I like Polymer80 pistol frames and knew that a slightly longer end mill would help people using a drill press, I sourced these specialized end mills to help and let me explain the features:

• The 9mm (0.393") cutting flute diameter is ideal for the channel work and is the same diameter of end mill that Polymer80 used to provide.
• The overall length of the end mill is 95mm (3.74"), longer than the original, and makes it easier to reach down into the barrel channel with a drill press with a big spindle.  
• The end mill is a four flute design to enable a smooth surface cut.  Normally you use 3 mill end flutes for finish machining plastic but since the Polymer80 frame work is very light, I opted for four flutes.
• It has a square head with a center cutting design which means you can do plunge cuts as well as sidways cuts with the mill.
• It's made from HSS-AL steel - W6Mo5Cr4V2Al to be exact - and will hold up just fine for doing these frames
• The end mill descriptor is 4F 9*10*45*95 HSSAL

When using an end mill, please understand they are not the same as drill bits.  The work piece needs to be secure and you remove a little bit of material at a time or your frame is going really want to jump all over the place.

ALWAYS WEAR EYE PROTECTION!

The price is per end mill and includes a plastic storage case for each.