Great looking set there. If I may add some pointers, this is for acrylic/resin pens wood would be a bit different. You appear to be a bit proud on some of your transitions. If you don't have a pair I would pick up a pair of calipers, Digital will be easier. I got mine at HF on sale for $9.99, picked up 3 at that price. When you open your components take your calipers, close them and zero out, and measure each piece (Nib, Band,Clip) and write down the measurements (I use mm) on a piece of paper or I use a Dry Erase board by my lathe. Turn your pen down to about +0.15mm of your finished size going by the measurements you wrote not the bushings. If you can, start WET sanding (never dry sand plastic) at 600. If you feel you need to start at a courser grit you can do 400 but I would not go lower just spend more time w/ the 400. If you need 400 I would leave it about 0.20mm to give you a little more room to clean up you sanding marks. Finish off w/ the 600 at about 0.08mm proud and move to your MM up to 12k. That will get you pretty darn close to zeroing out on your fit. You can use the MM if you want to get a little closer but be careful because Wet sanding removes material faster than you think. Once you finish with your MicroMesh you can, not necessary, take a fine plastic polish or fine car polish and give it a once over to remove the last of the micro scratches that you may be able to see.
Also, check out this link. It is a link to all of Kurt Hertzog's pen turning articles that he publishes in Woodturning Design, under the "Journey from Penturning to Penmaking". They are great articles. I still read them when I am having troubles becasue they will bring me back to the basics that I start to get away from.
Articles, Demos & Classes by Kurt Hertzog
Best of luck to you and keep it up. Can't wait for you next pen.
Ohh, if you like Slims try out the Trimlines(they go by several other names), same pen fatter centerband.
