You can buy a lead pointer for 2mm pencils to sharpen the leads on the Pentel 8 Color. The lead pointers are especially nice to create a very sharp point. Therefore, it makes making thin lines AWESOME! I highlight my scriptures by making an outline box around the verse instead of coloring over the text itself. Just do a search for "lead pointer 2mm". Also, the lead pointers vary in prices. You don't have get the most expensive one. The cheapie $1.00 lead pointers will work just as well. I DO NOT suggest getting the rotary type lead pointer. Tried it and it just does not work with the Pentel 8 Color. Get a lead pointer that looks just like a regular pencil sharpener (where you can actually see the blade).
The pencil refills are wonderful; I keep a spare set for when I run out. You can purchase individual colors for 2.04 from Pentel on line plus shipping; they even offer purple and other choices. You can buy just one color or buy them all individually. This is a great buy!
I have used the pen and these refills for years. They do not bleed through no matter what type of paper you are marking. They are very convenient. All in one pen. I highly recommend them. I do wish that I could find just the yellow refills. I use all the colors, but the yellow goes faster.