I have a bunch of different Taylor test kits and would recommend the "A" size for all chemicals except the R-0871-C and the R-0013-E.

I have found that the results with the FAS-DPD are much more consistent when using the 25ml sample size, therefore the bigger size of the R-0871.

I have also found the Rainbow Lifeguard #79 Kit for CYA to be easier to read which uses a 25ml sample with 25ml of R-0013 Reagent. (Taylor tells me it has a LONG shelf life if not abused).

As an aside for Richard --- I was wondering about buying the J (1/4 lb) of the R-0870 DPD Powder --- If I vacuum pack and/or freeze it will it keep??
I do a LOT of Chlorine Testing and have used 3 of the I size (10g) since late July.