Alex K showerhead diffusers are no doubt one of the best hitting diffusers available. The flame polished slits provide a smooth, drag-free hit, and they are a great upgrade for any tube. Each diffuser has a bushing 14-18mm joint and is signed Alex K 10 in titanium below the male joint. They fit in 18mm joints and require a 14mm slide. The diffusers are available in 4", 5", and 6" lengths (measured from the bottom end to the top of the male ground joint, including the joint in the measurement). There are only 4" diffusers still available.