A negative carrier adapter for Durst Femoneg carriers (those used in Durst 1200 for example). You need the Femoneg carrier itself – these are replacement adapters that insert into the Femoneg carrier. Photos of the Femoneg itself are for illustrative purposes to show how these adapters fit inside the carrier.
These were designed by me and are printed on demand using Atomic PLA on my modified Prusa MK3s 3D printers. They should bring you years of reliable use when using them for normal printing sessions as long as they are stored reasonably. Store them with your lenses (e.g. not in an attic on a hot summer South Texas day shoved in an unnamed box to be forgotten about for 20 years). Clean with a damp cloth optionally with alcohol (do not use acetone).