# Sandbox.ModelBuilder.WithMass

```csharp
ModelBuilder WithMass(float mass)
```

Sets the mass, in kilograms, used by collision shapes added directly to this builder.
The default is 1000.

### Parameters

- `mass` (`float`): The total mass of the collision body.

### Returns

`ModelBuilder`

Declared in [Sandbox.ModelBuilder](/api/Sandbox.ModelBuilder).
Assembly: `Sandbox.Engine`.