Eurorack

Eurorack is the 3U modular synthesizer format introduced by Doepfer and Analogue Systems in the 1990s.

Specifications
The format is based on IEC 60297 aka DIN 41494. The height of Eurorack modules is 3U (5.25" or 1.33.35 mm), that is three vertical units in a standard 19" equipment rack. Note also that the panels of the Euro format are often shorter than the 3U would suggest. This is not due to allowances for paint and fitting, (which is seen in many of the other formats), but rather due to a rim on the top and bottom mounting rails (produced by ProMA or Gie-Tec). These have a lip which uses some of the height. So Euro rack modules are often approximately 5mm shorter than the technically exact 3U height of 133.35mm (5.25"). Commonly 1/8" thick aluminium is used for the module panels.

The width of Euro modules is typically measured in "HP" (or "TE"); 1 TE/HP is equivalent to 5.08mm, or 1/5 inch. So a 24 TE/HP width is 24/5, or 4.8". In millimeters, it becomes 24 x 5.08, or 122mm.

Note that even though the height of both Frac Rack and Euro modules are 3U, differences exist in the mounting hardware. So, each format requires its own mounting system (screws, rails, etc).

Power requirements for Euro modules are usually +/-12VDC and 5VDC. Current draw depends on the module.

Euro modules typically use 1/8" or 3.5mm connectors and plugs for patching.

Mounting Screws
Most companies use an M3 sized screw with a typical length of 6mm that will extend to 10mm. Analogue Systems use M2.5 for their cases. Doepfer specifications call for M3x6mm size screws. Elby racks call for M3x8mm size screws. Monorocket cabinets use sliding nuts in their rails, threaded to accept 4-40 screws.