This is a bolt on GoPro Session Mount for the Armattan Beaver frame. The Session mount works with or without a ND filter inserted into the lens. ND filters are sold separately. The mount is intended to be used with a ND filter. If you decide to not use a filter inside the front of the mount the Session will be slightly loose inside the print but will still work as intended.Printed out of TPU and available in a variety of colors.