21329 Adapter for Sub-Speaker M20 Thread to 35mm 250mm LongFor speaker satellite systems. The short 250 mm adapter is perfectly suited as a single rod or as an extension rod. The adapter with a tube diameter of 35 mm has a M20 male threaded bolt on the one end and a M20 female thread on the other end. With the adapter the rod can be expanded to any length. Product Features Perfectly suited as a single rod or as an extension rod M20 male threaded bolt on the one end and a M20 female thread on the other end