500 Series Modules & Racks
The 500-Series standard for compact professional audio modules and powered racks (or lunchboxes) was developed some years back. Pro audio manufacturers realized that the form factor and relatively economical price of the modules (since you don't have to buy an enclosure and power supply for each module), could open up new avenues for pro and project studios and we now have a large variety of gear available in this professional outboard gear format.
500 Series modules cover the usual categories: mic preamps (often with a d.i.), graphic and parametric EQs, compressor/limiters, tape emulation and to a lesser extent, delays and reverbs!
The most popular form factor for powered 500-series racks is either a 6-space rack (the so-called lunchbox) or a 10-space rack. There are also 8-space 500-series powered racks that incorporate master sections. Tidepool Audio carries powered 500-series racks from RND, Lindell and Radial.