This is a waterproof commercial log book for pool and spas. Each page contains two grids which you can specify date and day. Each grid has a field for readings every two hours starting at 5 AM and ending The following items can be recorded: FAC, TC, CC, TB, ORP, pH, ALK, CH, Backwash, Strainer, Drain Coves, H20 Clarity, H20 temp, Weather Conditions, Bather Load, Flow Rate, Pressure, Addl Readings, Initials. The book has 94 pages with two days worth of recording on each page. THIS ITEM IS NON-RETURNABLE.