Yes, I heard about Bully Sticks on Yorkietalk, and they're a favorite of Joey's. I did learn that Bully Stick is a generic term, and any company can call itself that. A bully stick should be 100% digestible, and is made from beef tendons, which are made from a bull's penis. It's important that these are dried properly, and some bully sticks use preservatives, and have expiration dates. I've only used Merrick Bully sticks, and you can occasionally find them on eBay, for a little more than $2.00 a stick, there are no added preservatives, and no expiration date, a product that is properly dried doesn't need one because the drying process acts as a preservative. A 6-inch stick lasts all week and he chews on it all the time, they are very hard, and I believe that they help the teeth and gums stay healthier. The evening seems to be his favorite time, and we usually have to hold it while he chews on it. (I've spoiled him.) Be cautious with sticks, with price increases many companies are importing them to compete, and many of the imports are probably coming from China. Here's a link to the Merrick company, but you can find them on eBay, and Amazon for less.
Merrick Pet Foods - Dog Treats