For what its worth...I use Modern Cure#1 in my curing...And they don't say it, but these amounts are for a rub and not a brine.
Source...
The National Center for Home Food Preservation
Guide and Literature Review Series:
Smoking and Curing
2.3. Cure Mixtures
For the home food preserver, measuring small batches of cure for nitrites or nitrates would require an analytical scale that few consumers have access to. Therefore, some manufacturers sell premixed salt and nitrate/nitrite curing mixes for easy home use. Caution is needed when using pure saltpeter instead of commercially prepared mixes, since accidental substitution of saltpeter for table salt in recipes can result in lethal toxic levels (Borchert and Cassens 1998).
Some examples of commercially prepared cures include:
2.3.1. Prague Powder #1, Insta Cure, or Modern Cure.
This cure contains sodium nitrite (6.25%) mixed with salt (93.75%). Consumers are recommended to use 1 oz. for every 25 lb. of meat or one level teaspoon of cure for 5 lb. of meat.
2.3.2. Prague Powder #2
This mix is used for dry cured meats that require long (weeks to months) cures. It contains 1 oz. of sodium nitrite and 0.64 oz. of sodium nitrate. It is recommended that this cure be combined with each 1 lb. of salt and for products that do not require cooking, smoking, or refrigeration. This cure, which contains sodium nitrate, acts like a time-release cure, slowly breaking down into sodium nitrite, then into nitric oxide. The manufacturer recommends using 1 oz. of cure for 25 lbs. of meat or one level teaspoon of cure for 5 lbs. of meat.