Answer: Both TWP 1500 and TWP 100 will provide the same protections.
TWP 100 Stain has a V.O.C. of 550 grams/liter. Certain states now require lower V.O.C. limits in wood preservatives (350 gram/liter). TWP 1500 Stain is the same base formulation as TWP 100 Series with minor formulation changes to comply with the state regulations.
The same color choices come in both series with the exception of the Black Walnut (1500 series only) and the Cape Cod & Prairie Gray (100 Series Only)
TWP 1500 Series will go on over the 100 Series as long as it has been a year since you last stained the deck.
TWP 100 Stain can not be shipped to CA, CT, DC, DE, IL, IN, ME, MA, MD, NH, NJ, NY, OH, PA, RI, VT, VA and CANADA due to VOC regulations.