Microsoft Natural Ergonomic 4000 (B2M00012).

My neurologist recommended this keyboard to me as I have had difficulty with the flatbed and slightly raised ones I had bought over the past 3 years. I have carpal tunnel syndrome in both wrists and arthritis in both hands and spend about 5-6 hours a day on the computer. The ease of use and COMFORT in using this keyboard is outstanding! It has larger than normal hot keys, a comfortable wrist guard, back and forward buttons, and a centrally placed Zoom feature - something I've never seen on other keyboards. This Zoom function is a boon for the sight impaired, whether you just need reading glasses or heavier. However, the keyboard is very hard to clean, the larger keys make for larger spaces for dust and dirt to harbor. All in all, the pros outweigh the con. I can now work with only 3 breaks needed compared to the 7 I usually worked in a 6 hour day!