Level of Development is one of the most misused terms in BIM. It is often treated as a measure of how detailed a model looks. It is not. LOD describes how much you can rely on the information in an element, which is a different and more useful idea.
The distinction that matters
A model element can look extremely detailed and still be unreliable, because the geometry was drawn approximately for visual purposes. LOD is about reliability, not appearance. It tells the person downstream how far they can trust what they are reading.
LOD 200: approximate
Elements are generic placeholders with approximate size, shape, location and orientation. A wall is roughly in the right place with roughly the right thickness. You can use this for early coordination, spatial planning and preliminary quantities, but you cannot dimension from it or order anything.
LOD 300: specific and dimensionable
Elements are modelled as specific assemblies with accurate size, shape, location and orientation. You can take dimensions directly from the model and rely on them. This is the level most construction documentation works at, and the level most coordination is genuinely useful at.
The important shift from 200 to 300 is that measurements become trustworthy.
LOD 350: coordinated with neighbours
Everything in 300, plus the interfaces with other systems. Supports, connections, hangers, penetrations and the things that make clash detection meaningful. A duct at 300 is accurately sized and placed; at 350 it carries the hangers and the sleeve through the wall.
If you are running serious multidisciplinary coordination, 350 is usually what you actually need. Coordinating at 300 finds the obvious clashes and misses the ones that cost money on site.
LOD 400: fabrication ready
Detailed enough for manufacture and installation, with the specific information a fabricator needs. This is typically produced by trade contractors rather than the design team, and modelling to 400 when nobody needs it is expensive.
Practical points
LOD varies by element, not by model. A project is rarely uniformly at one level. Structural frame might be at 350 while interior partitions sit at 300 and landscape at 200. Specify by system and by stage.
Higher is not better. It is more expensive and slower. The right level is the one that supports the decisions being made at that stage.
Write it into the BIM execution plan. Disputes about model reliability almost always trace back to an assumption that was never written down. A short matrix of system against stage against LOD prevents most of them.
When commissioning modelling work, state the LOD you need per system rather than asking for a detailed model. It is the difference between a clear brief and an expensive misunderstanding.