Long story short, if you're looking for an arm to attach an extra tom (or otherwise!) too, this is the one. Period.
There are many arms and what-nots to attach other what-nots to more what-nots, but Gibraltar are the perfect ones. This fits on any standard rack and will not budge. It will also can adjust to pretty much any position you want with great ease and stability. This arm will not move anywhere when you hit whatevers on it! It has also lasted longer than most of my hardware! Gibraltar, you guys are the Bee's Knee's.