Get the Most out of Your Test Kit – Extend the life of your pool or spa test kit with this Thiosulfate N/10 0.75 ounce dropper refill. This is an easy-to-use test reagent for Total Alkalinity, a common water test parameter. Quick & Easy to Use – Simply collect your water sample using the comparator and add the appropriate testing reagents to determine the results. Product instructions are written in non-technical language with easy-to-understand pictograms. Pool & Spa Test Kits Built to Last – With testing kits built to last, you’ll find yourself needing to replace your Taylor reagents before the entire kit. Replacement reagents are available separately so you can easily replace your pool and spa testing chemicals every season. For Homeowners and Professionals – Taylor products are built to professional standards but with processes easy enough for any pool or spa owner to use. With unparalleled customer service and support, Taylor is the go-to for every distributor, retailer, commercial operation, and homeowner… wherever water is tested. Proudly Made in the USA – Since 1930, Taylor has been the leading developer of water testing products. All Taylor products are engineered and manufactured in the USA. You can trust that when you choose Taylor, you will receive the highest quality water testing equipment on the market.