FiveFish Audio - DIY Mic Preamp Kits, 500 Series Kits, VPR Certified
PR502 2-Slot 500-Series Chassis Kit with External Power Supply – DIY Recording Equipment
Racking 500 Series/Lunchbox Preamps, Equalizers, Compressor Modules: How to Instructions. – FiveFish Audio Blog
Amazon.com: Hudson Hi Fi 1U 500 Series Universal Blank Panel, Rack Mount Spacer for 19 inch, Breaker Filler Plate made from Steel, Black Matte Finish, 1 Pack : Musical Instruments
Choosing A 500-series Chassis
500 Series Rack - 500 Series Chassis - 500 Rack - Vintage King
GroupDIY 51x Alliance Racks (API 500 series compatible) - Gearspace.com
21 DIY Kit Sources for Pro Audio, Synth Modules & Instruments — Pro Audio Files
Building your own affordable vintage audio gear - Optoproductions