This genuine Blackmagic Design thumbscrew is a replacement for the URSA Viewfinder's 1/4in-20 mounting point. It tightens and releases by hand, letting you fit or remove the viewfinder without tools, and it's worth keeping a spare in the kit. Blackmagic also makes a 3/8in version, so check which thread your mounting point takes before ordering.

Key features

• Genuine Blackmagic spare part for the URSA Viewfinder.
• 1/4in-20 thread.
• Tool-free — tightens and releases by hand.
• Matching 3/8in version available for the larger mounting thread — check your mount's thread before ordering.