SphereCollider defines a sphere shape for collision. The size of the sphere is determined byRadius and the Transform's Scale .
(NOTE) Recommended Reading: The Collider page should be read before this page.
Radius
A SphereCollider exposes the Radius property which determines the pre-transform radius of the sphere. The SphereCollider will always be a perfect sphere, even when non-uniform scale is present. It does this by taking the largest scale value to determine the radius in world-space.