Double Arm Set (for Narrow Mount Extension Kit) - 31.8mm Only Parts to expand the clamp section of Type 19 and narrow mounts by replacing some parts. I used this in combination with Type 19 to mount my smartphone. A separate adapter such as a smartphone case is required. There seem to have been screws included with the original product, but they are missing. It can be attached with the screws from Type 19. A smartphone ring is included as a bonus. Thank you for your interest. Thank you for looking.