I've been cutting/trimming my own hair ever since I was a young boy in middle school. My brand of choice when it comes to tools are Andis products. I use Andis trimmers and clippers because they are the most recognized by professional barbers and have the highest quality standards.
Andis 29775 11-Piece Home Hair Cutting Kit
So I was in the market for a new trimmer blade, but the model [above] I had was old and isn't made anymore [if it is, I sure as heck couldn't find it]. So since I had an old model and no where could I find a replacement blade, I decided to just go ahead and upgrade to a new model. The well known Andis T-Outliner [$45-65] which is the best you could buy in the Andis line.
The trimmers are phenomenal and a great investment for any man not just African American. The blade comes super sharp and should last that way if they kept super lubricated and cleaned afar each use. I use them for dry shaving and cleaning up my edges. I have to use them everyday since my hair grows back super fast.
The price is a little steep for a pair of trimmers, but they will pay for themselves after about 3 months. If you go to the barbershop every other week like I used to back in the day, you will know what I mean.