These are M4 Clearance Inside Diameter spacers / stand off collars with a 6mm Outside Diameter. These are manufactured in-house from Brass using
【Product Name】:M4 x 50mm + 6mm Hex Standoff Spacer. 【Thread Size】: M4,Single hex head with male female type screw threaded, Material: Brass, Color
Male to Female Thread Spacer Screws Brass Hex Standoff M4 x 50mm + 6mm PCB Pillar for Drone Quadcopter, Computer & Circuit Board, Pack of 15: : Industrial & Scientific
M4 Male x M4 Female Brass Hex Standoff Spacer - 5mm to 25mm
Pololu 1972 - Nylon Spacer: 6mm Length, 4mm OD, 2.7mm ID (50-Pack) - Kamami on-line store
Spacers and Standoffs in Pune, स्पेसर, पुणे, Maharashtra
Round Spacers M3/M4/M5/M6/M8
Brass Material, Hex Head, Female Type Threaded Rod Pillar Standoff., Ideal for coupling use.
M4 x 8mm Female Threaded Brass Hex Standoff Pillar Rod Spacer Coupler Nut 25pcs
WHITE Nylon SPACERS
M12 X 25MM OD Stainless Steel Spacer - Standoff Collar Stand off Spacers £2.65 - PicClick UK
10/50pc Solid Brass Copper M2 M2.5 M3 M4 Hex Standoff Hexagon Pillar M-F F-F Male-Female Female Spacer for PCB Board Motherboard - AliExpress
Jinzhaolai M2 M2.5 M3 M4 Hex Brass Male Female Standoff Board Rack Stud Hexagon Threaded Pillar Pcb Column Motherboard Spacer Bolt Screw