The K2005 and K2006 are identical, except for the chlorine test. If chlorine levels are 5 ppm, both kits will show 5 ppm; but if levels are 10 ppm, the K2005 will still show 5 ppm, but the K2006 will show 10. It gets worse: if chlorine levels are 20 ppm, the K2005 will show ZERO, but the K2006 will show 20.

Since you have to have high levels of chlorine to manage algae in outdoor stabilized pools . . . . this is a problem.

As Mom said, get the K2006 (A model = 3/4 oz bottles; C model = 2 oz bottles.)