The 3-WAY and 6-WAY kits offer a choice of N,N-diethyl-pphenylenediamine (DPD) or orthotolidine (OTO) for determining sanitizer residuals. The 9-WAY kit uses the DPD method exclusively and includes tests for calcium hardness and the stabilizer level in water treated with cyanuric acid, pool/spa dosage charts, and a copy of I Never Liked Chemistry. This booklet uses illustrations and simple vocabulary to turn a complex subject into one that is easy to understand.