These are M4 Clearance Inside Diameter spacers / stand off collars with a 6mm Outside Diameter. These are manufactured in-house from Brass using
Pololu - Nylon Spacer: 6mm Length, 4mm OD, 2.7mm ID (50-Pack)
Spacers and Standoffs in Mumbai, स्पेसर, मुंबई, Maharashtra
1502 Series 4mm ID Spacer (6mm OD, 27mm Length) - 4 Pack, goBilda GB-1502-0006-0270
Specification: thread size: M4 male female 5mm+6mm; overall size(approx): 11 x 6mm/0.43x 0.24 (L*Max.D); material: brass; color: gold tone; net
uxcell 30PCS M4 x 5mm + 6mm Male-Female Thread Brass Spacer Standoff Hexagonal Hex Standoff Spacer for DIY Computer Build, Electronic Projects, PCB Circuit Board : Industrial & Scientific
KOVNOVI 50pcs M4*L+6mm Brass Standoff Spacer Male Female Nickel Plated Spacing Screws Threaded Pillars 4mm Hex Stud PCB Board (Color : 50mm, Size : M4) : Industrial & Scientific
Uxcell ABS ID 4.2mm OD 7mm Length 8mm Round Spacer Black 300 Pack
2MM Threaded M2 Anodized Stack Spacer (5 Pcs.)
Specification: thread size: M4 male female 5mm+6mm; overall size(approx): 11 x 6mm/0.43x 0.24 (L*Max.D); material: brass; color: gold tone; net
uxcell 30PCS M4 x 5mm + 6mm Male-Female Thread Brass Spacer Standoff Hexagonal Hex Standoff Spacer for DIY Computer Build, Electronic Projects, PCB Circuit Board : Industrial & Scientific
Male to Female Thread Spacer Screws Brass Hex Standoff M2 x 6mm + 4mm PCB Pillar for Drone Quadcopter, Computer & Circuit Board, Pack of 20, Gold: : Industrial & Scientific
M2 Aluminum Spacers, 10 Pcs Metal Spacer Aluminum 2.1mm ID x 4mm OD x 2.5mm L
M4 Male x M4 Female Brass Hex Standoff Spacer - 5mm to 25mm
