I normally use the blue chorine/ph test kit for FC during the week for quick check and the TF-100 kit test on weekends. Ran out of R-0600, and pool store says OTO-1 is the same (1 oz bottle, but only $2.). The R-0600 says "<10% Hydrochloric acid"; the OTO-1 says "5.14% Hydrochloric acid". Close enough?
Also bought a case (4 gallons) of Muratic acid for $17.50, bargain compared to Home Depot where I'd been getting it, same 31% (box is labeled Hydrochloric Acid, bottles are labeled Muratic acid). Just curious if this could be diluted say 5:1 with water, and used as 6% acid for the test kit. I'd probably never bother to do this... just a thought.