It's not a traditional multitool, in that it's composed of three separate parts that interlock in different ways to perform 15 different functions. Plus the whole thing is designed to fit inside Magpul MOE and MIAD pistol grips for MSRs.
There are a lot of multi-tools out there designed for firearms, especially MSR platform rifles, but they're mostly built around a pair of spring-loaded pliers, which are of limited gun-specific use. Besides, most people who already carry a multi-tool don't need another set of pliers.
That's the innovative thing about the Short Stack—it's built around wrenches, not pliers, which are very useful to an MSR shooter and are hardly ever along in the field or at the range, let alone on-board the gun. This tool has four wrenches sized for flash hiders and other common accessories, in addition to a specific wrench for tightening or loosening a buffer tube, all stored inside an already-hollow pistol grip, along with two double-sided bits.
The company calls it a "solid state" tool, borrowing from the tech world, which, in this case, means there are no hinges and no springs involved.
The Short Stack also includes a front sight adjustment tool, a pull-through handle for cleaning cables like the ones OTIS makes, and scraping tools shaped for an MSR's firing pin, bolt, and bolt carrier.
The tool is also compatible with Magpul M-LOK handguard accessories, including a 7mm wrench and two-sided hex bits for M-LOK fasteners.
Other functions include a windage/elevation sight tool, a 4mm Torx driver, a #0 cross driver, a 1/2" wrench, a 1/4" wrench, a 3/8" wrench, and a 3/4" wrench—and every tool is clearly labeled with laser etching.