The origins of Modulex trace back to the early 1960s and to Godtfred Kirk Christiansen, then managing director of The LEGO® Group and son of the founder, Ole Kirk Christiansen. While working on the design of a real building, Christiansen attempted to use standard LEGO® bricks to create a scale model. He quickly discovered a fundamental limitation: traditional LEGO® bricks were not true cubes. Their proportions (roughly 5:5:6) made precise architectural scaling difficult and inaccurate.

To solve this problem, Christiansen commissioned the development of a new type of brick with perfectly cubic proportions. The result was a brick measuring 5 mm × 5 mm × 5 mm, forming a true 1:1:1 ratio. This new system allowed architects to build accurate scale models—most commonly at 1:20 scale—and to translate models directly into real‑world dimensions.

In 1963, the LEGO® Group introduced this system under the name Modulex and was sold as professional modeling tools rather than toys. They were marketed primarily to architects, planners, and industrial designers. Unlike standard LEGO® sets, Modulex bricks were not compatible with LEGO® System bricks. They were offered inmuted, construction‑oriented colors and designed to be cut, glued, marked on and permanently assembled. They were supplied in parts packs rather than play sets and were marketed as the M20 System, referencing their 1:20 scale.

In 1965, Modulex was formally separated from the LEGO® Group as an independent company, Modulex A/S, headquartered in Billund, Denmark. At this point, the branding changed as the word “LEGO” was removed from the studs and replaced with a simple “M” to emphasize Modulex’s professional identity.

While the bricks themselves never achieved widespread adoption among architects, the M20 system led th;e company to find its niche in the signage industry and transitioned away from bricks and toward modular information systems such as planning boards, control panels and visual management systems. Modulex stopped making bricks in 2004 and The LEGO® Group purchased back the license to make Modulex bricks in 2014, however, they have not revived it yet. Today, Modulex A/S is one of the largest and most successful providers of architectural signage and visual communication solutions in the world.

Modulex Color List:

Modulex Color Name	Closest LEGO Color	Modulex Color Code
MX White	White	1, 31 or 80
MX Light Bluish Gray	Light Bluish Gray	32
MX Light Gray	Light Gray	2
MX Charcoal Gray	Dark Bluish Gray	40
MX Tile Gray	Dark Gray	Unknown
MX Black	Black	3 or 81
MX Tile Brown	Dark Brown	Unknown
MX Terracotta	Fabuland Brown	4
MX Brown	Dark Tan	9
MX Buff	Tan	5
MX Red	Rust	13
MX Pink Red	Salmon	33
MX Orange	Earth Orange	12
MX Light Orange	Light Orange	39
MX Light Yellow	Bright Light Yellow	35
MX Ochre Yellow	None	6
MX Lemon	Medium Lime	15
MX Pastel Green	Lime	14
MX Olive Green	Sand Green	7
MX Aqua Green	Light Turquoise	34
MX Teal Blue	None	8
MX Tile Blue	Blue	Unknown
MX Medium Blue	Medium Blue	38
MX Pastel Blue	Maersk Blue	11
MX Violet	Sand Purple	37
MX Pink	Medium Dark Pink	16
MX Clear	Trans-Clear	0 and 10
MX Foil Dark Gray	Dark Gray	82
MX Foil Dark Green	Dark Green	84
MX Foil Light Green	Light Green	85
MX Foil Dark Blue	Blue	86
MX Foil Light Blue	Light Blue	87
MX Foil Violet	Purple	88
MX Foil Red	Dark Red	89
MX Foil Yellow	None	90
MX Foil Orange	Light Orange	91

 

Part	Part #	Size
1x1 Brick	1111	5x5x5mm
1x2 Brick	1121	5x5x10mm
1x3 Brick	1131	5x5x15mm
1x4 Brick	1141	5x5x20mm
2x2 Brick	1122	5x10x10mm
2x3 Brick	1132	5x10x15mm
2x4 Brick	1142	5x10x20mm
1x5 Brick	1151	5x5x25mm
2x5 Brick	1152	5x10x25mm
1x10 Brick	1110	5x5x50mm
2x20 Brick	1140	5x10x100mm
2x8 Brick	1182	5x10x40mm