Guide Star Ring for Astronomical Photography
3 - point fixing ring (single ring), multiple specifications available, metal structure with sandblasting and oxidation, 14MM widened frame, three locking screws with protective heads to prevent scratches, bottom plane installation without slipping, and more stable bottom plane connection. 
 Metal Structure/Thickened Adapter Ring
Three locking screws with protective heads to prevent scratches / 14MM widened ring surface, more contact surfaces and more stable.