Custom Unity Handles - `HandlesExtensions.DrawSolidHollowDiscArc(...)` - Just like `Handles.DrawSolidDisc` but has a inner and outer radius for hollow discs: http://docs.unity3d.com/ScriptReference/Handles.DrawSolidDisc.html

Handles.DrawSolidHollowDiscArc.cs

using UnityEngine;
using UnityEditor;
using System.Collections;
using System.Reflection;

using self = HandlesExtensions;

public class HandlesExtensions {
	
	static PropertyInfo handlesHandleWireMaterial_PropertyInfo;
	static MethodInfo handleUtilityApplyWireMaterial_MethodInfo;

	static HandlesExtensions() {
		BindingFlags bindingFlags = BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static | BindingFlags.FlattenHierarchy;
		self.handleUtilityApplyWireMaterial_MethodInfo = typeof(HandleUtility).GetMethod("ApplyWireMaterial", bindingFlags);

		self.handlesHandleWireMaterial_PropertyInfo = typeof(HandleUtility).GetProperty("handleWireMaterial", bindingFlags);
	}

	static void DrawSolidHollowDiscArc(
		Vector3 position,
		Vector3 normal,
		Vector3 alongPlane,
		float angle,
		float innerRadius,
		float outerRadius
	) {
		if (Event.current.type != EventType.Repaint) {
			return;
		}

		int numSamples = 60;
		
		Shader.SetGlobalColor("_HandleColor", Handles.color * new Color(1f, 1f, 1f, 0.5f));
		Shader.SetGlobalFloat("_HandleSize", 1f);
		if(self.handleUtilityApplyWireMaterial_MethodInfo != null) {
			self.handleUtilityApplyWireMaterial_MethodInfo.Invoke(null, null);
		}
		else if(handlesHandleWireMaterial_PropertyInfo != null) {
			((Material)handlesHandleWireMaterial_PropertyInfo.GetValue(null, null)).SetPass(0);
		}


		GL.PushMatrix();
		GL.MultMatrix(Handles.matrix);
		
		GL.Begin(GL.TRIANGLES);

		alongPlane.Normalize();
		Vector3 outerArcEdge = alongPlane * outerRadius;
		Vector3 innerArcEdge = alongPlane * innerRadius;
		for (int i = 0; i <= numSamples; i++) {
			Quaternion rotation = Quaternion.AngleAxis((((float)i)/numSamples)*angle, normal);
			Vector3 outerVertice = position + rotation * outerArcEdge;
			Vector3 innerVertice = position + rotation * innerArcEdge;
			
			Quaternion rotationNext = Quaternion.AngleAxis((Mathf.Clamp((float)i+1, 0f, numSamples)/numSamples)*angle, normal);
			Vector3 outerVerticeNext = position + rotationNext * outerArcEdge;
			Vector3 innerVerticeNext = position + rotationNext * innerArcEdge;

			GL.Color(Handles.color);
			// 1____2
			//  |  /
			//  | /
			// 3|/
			GL.Vertex(outerVertice);
			GL.Vertex(outerVerticeNext);
			GL.Vertex(innerVertice);

			//    /|2
			//   / |
			//  /  |
			// 1‾‾‾‾3
			GL.Vertex(innerVertice);
			GL.Vertex(outerVerticeNext);
			GL.Vertex(innerVerticeNext);
		}

		GL.End();
		GL.PopMatrix();


	}
}