The OTO kit is fine for daily testing. Unless your chlorine levels are higher than 5 (like if you are shocking the pool or run a high CYA/high cl pool), you can use the OTO for quick checks. I use my OTO kit frequently. The K-2006 (not 2600) is used for when you need to test everything including your CYA or if you need to test for high chlorine levels or to find out if you have an CC.

BTW --- I just checked the Amazon links. Apparently, Amato Industries is sold out today of the K-2006 but they do show the K-2006C as being in stock. That one is actually a better buy. However, if you prefer the K-2006, try back in a day or so. They seem to quickly restock.

Do us a favor, please. To make it easier for us to help, if people will create a signature line with their pool specs, it keeps us from having to reread through posts to find out basic information. You can create a signature by clicking on 'settings' in the upper right-hand corner of the homepage. In your sig, please put type of pool, volume, type of filter, size of pump, whether or not you have a SWCG or any water features and the fact that you do or do not have a K-2006. Thanks!