those arn't all that, the tool is good and you'll find it easy to get in and around the port without snagging it but ali will clog those pink stones allmost instantly and will end up useing the sanding rolls, those cheep tungsten carbide bits on ebay will shift metal a lot faster and last much longer than stones, those tungsten carbide burrs one ebay with one of those clarke engraveing tools should work, think they were both 1/8" to rip round ports my top favoret is a 1/4" shaft bur on cheep electric drill then do the delicate stuff with a smaller machene, only problem with that is snagging a 1/4 burr is not good news