# One

> Bit #0 set (1) in the PhysicsMask. The remaining bits are reset (0).

## Definition

* **Type:** Field
* **Namespace:** [Unity.U2D.Physics](/engine/6000.5/script-reference/unity/u2d/physics.md)
* **Assembly:** UnityEngine.PhysicsCore2DModule

```csharp
public static readonly PhysicsMask One
```