This round folding arm clamp adapter is designed for use with carbon tubes in RC quadcopter and multi-rotor drone frames.Made from CNC-machined aluminum and finished in black, it supports tube diameters of 20mm, 30mm, and 40mm, with a 4mm mounting hole.The 20mm version allows a folding angle of approximately 170 degrees, supporting both horizontal and vertical configurations.Versions for 25mm to 40mm tubes typically provide a 90-degree folding angle, with the 30mm horizontal configuration offering 160–170 degrees.Specific dimensions include: 25mm variant with 29mm outer diameter and 25mm inner diameter; 30mm variant with 30mm inner diameter; 35mm variant for 35mm outer diameter tubes; and 40mm variant with 44mm outer diameter and 40mm inner diameter.This component is intended for use in compatible drone frame assemblies.