The CollisionGroupId property describes the ID number of the part’s collision group. Parts start off in the Default group whose ID is 0. Although this property can be directly changed, it is recommended to instead manipulate the collision group of a part using the name of the group with the
/PhysicsService/SetPartCollisionGroup function. You can find the ID of a collision group by using
This value cannot be negative, and cannot exceed
/PhysicsService/GetMaxCollisionGroups. Invalid IDs are clamped.