What the thread found

• Tiffen manufactures an adapter arm post (part number 250-7975) that converts Master/Ultra gimbal heads to work with EFP/3A/PRO arms, priced at $175, but this adapter cannot be used in reverse
• The correct bore specification for Master/Ultra size gimbal adapters is 0.740 inches with tight tolerances of plus 0.000 and minus 0.002 inches after anodizing
• Custom machinists including those at Bees Engineering and Skipps Engineering Enterprises can fabricate arm post adapters to specification
• An adapter arm post can be designed with a stepped diameter, using 5/8 inch bore for two-thirds of the length and Master size bore for the final third to fit into the gimbal

Depends on

• Tiffen's standard adapter works only in one direction and cannot be reversed for opposite compatibility
• Availability of custom-made adapters depends on individual machinists maintaining stock or willingness to produce new batches
• The thread is from 2006 and contact information for some suppliers may no longer be current

Parts

Arm Post

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