Eurorack

Euro is a modular synthesizer format. The height of Euro format synthesizer modules is equal to three vertical units in a standard 19" equipment rack. This standard height is called "3U". Euro format modules typically use 3.5mm (1/8") connectors and plugs for patching.

Manufacturers
Analogue Solutions (UK)

Analogue Systems (UK)

Bananalogue (USA)

Bubblesound (US)

Cwejman (Germany)

Cyndustries (USA)

Doepfer (Germany)

Elby Designs (Australia)

Flight of Harmony (USA)

Future Sound Systems (UK)

Harvestman (USA)

Livewire (USA)

Malekko Heavy Industry (USA)

Makenoise (USA)

Metasonix (USA]

MFB (Germany)

STG Soundlabs (USA)

Tip Top (USA)

Module Depth
(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