The RSX stem is designed to be bolted directly onto the top crown of RockShox Boxxer downhill forks and is fully CNC machined from 6061-T6 alloy.
The stem features a 30-degree rise and can be run at either 45mm or 50mm reach. Funn makes a similar stem (the MZX) to fit Marzocchi's 888 downhill forks.
Feel is super-stiff and by using titanium front-clamp bolts, the weight is kept down to a skimpy 185g. Subtract the grams you save by being able to chop down your steerer and the RSX makes a lot of sense.