There is no real difference between the bear spray needed for a certain kind of bear. Grizzly bear spray will work equally well for black bears, and even other animals such as cougars. What makes spray suitable for a bear to begin with is that it puts out a lot of spray, and the spray goes a long distance. You want to be able to convince the bear, before it gets close, to go elsewhere. As long as your bear spray is able to do that, it will be suitable for any kind of bear.
Grizzly Bear Spray
What to look for when you want grizzly bear spray.
Can Size – The bigger your can of bear spray is, the more spray you will have to work with. And if you have a larger can you will be able to spray for longer. Bigger cans can also sometimes spray a bit farther, and when a bear is coming towards you at a run, every foot of distance is very important.
Holster – A can of bear spray that is not accessible is worthless to you. You might not have much time to react to a bear, especially a more aggressive bear like a grizzly. So a holster or something else that makes your bear spray accessible at all times is just as important to have as the bear spray itself.
Best Grizzly Bear Spray
There aren't many, but these are the best options for grizzly bear spray.
Counter Assault Bear Deterrent Spray (230 g) - This the slightly smaller size of bear spray can made by Counter Assault. It's range is between 12 and 30 feet, and it sprays for approximately 7 seconds, which is more than enough when a grizzly is charging at you. You might also want to consider a holster.
Counter Assault Bear Deterrent Spray (290 g) - The larger of the two canisters made by Counter Assault, this one will go for slightly longer, at 9.2 seconds of spray time, and also has a slightly larger range, at anywhere from 12 feet to 32 feet. Again, it's a good idea to consider getting a holster so you have somewhere convenient to put the spray.
Frontiersman Bear Spray - The Frontiersman bear spray can is slightly smaller than the two from Counter Assault, at just 225 grams. It comes with a holster, however, which is a smart piece of equipment to have. It will fire approximately 18 feet, so a shorter range of fire, and will spray for 8 seconds, so about the same as the two Counter Assault options.