The Rolls MX41s is a passive stereo (and mono) 4-channel mixer. It is small, less than the size of a standard guitar pedal, and it has 4 passive volume controls for the 4 inputs, and a single output. All of the connections are 1/4 inch. It weighs 1 lb, and it feels and looks solid, just like all Rolls products. When all the knobs are turned up, it can also be used backwards as a signal splitter.
The Rolls MX41s works with both stereo and mono signals, but not a combination of the two. This mixer is great for expanding a regular console mixer, when you run out of inputs. Also, with the proper adapters, you can convert a stereo signal into a balance-mixed mono signal with this device. The level knobs on the front feel solid, but they are a little hard to see their levels at a distance; there is a little indentation on the knob that marks it's location, and it's hard to see. Reminds me of the knobs on a Mesa Boogie amplifier, which are impossible to see from a distance.
All of the connectors are gold, so the sound quality is great; I've never had any noise or signal degradation problems with this mixer. Just don't expect it to do something that it can't do, like handling unusual signals such as balanced, mic, or speaker. Because it's passive, you have to remember that this mixer is incapable of increasing a signal's volume, it has no amplification abilities.
Overall, the Rolls MX41s is a great little box that has many uses, especially around guitar rig setups, stage setups, studio setups, and so on. If you've ever tried mixing signals together with a splitter cable, a dedicated box like this will sound much better, not to mention the flexibility of level adjustment. Rolls are masters at making small boxes that do little things, but I find their products to always be solid and useful.