Eurorack

Euro is a modular synthesizer format, (sometimes called "Eurorack").

The height of Euro format synthesizer modules is 5.25", which is equal to three vertical units in a standard 19" equipment rack. (This standard height is called "3U".) 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 the shape of the top and bottom extrusions used by PROMA. These have a lip which "uses up" some of the height. So the Euro rack modules are often some 5mm shorter than the technically exact 3U height of 133.35mm (5-1/4"). (Excerpted from Randall's excellent post at the Electro-Music modular forum.)

Euro modules typically use 3.5mm connectors and plugs for patching. Power requirements for Euro modules are usually +/-12VDC and 5VDC.

Euro module widths are 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=122mm. (Excerpted from Randall's excellent post at the Electro-Music modular forum.)

Refer to the List of Modular Synth Equipment Manufacturers page for a list of Euro module manufacturers.

Module Depth
Following is a list of Euro module depths. This information is important when purchasing or planning construction of a case or rack for your modules. (courtesy of felix, from this thread)

Livewire  Frequensteiner - 1.50" (38.1mm) Dual Cyclotron - 2.25" (57.15mm)

Plan B  Model 28 - 2.50" (63.5mm) Model 15 - 1.75" (44.45mm) (MKII, MKI is much deeper) Model 14 - 3.75" (95.25mm)

The Harvestman  Tyme Sefari - 2.00" (50.8mm) Malgorithm - 1.50" (38.1mm)

Doepfer