Item Descriptions:-Dimension: Thread: M6; Thread length: 35mm/1.37inch; Head size: 20 x 20 x 4 mm/0.78 x 0.78 x 0.15inch-Application: The automatic T-slot of the roof box is very fit for the holder and fixes the roof box. It can be used with a sliding system on many carriers. It also can be used to attach bike carriers, ski holders or roof boxes.-Square Base: The size of the roof box adapter square head is about 20x20mm, and the large area can withstand the pressure exerted by the roof box. Easy to install, just install in the socket and use.-Material: Made of 304 stainless steel, its characteristic is strong, corrosion resistant, wear-resistant and rust-proof.-What you get: The package includes 6pcs T-slot slot blocks roof bars.Package:6x T-slot AdaptersItem Specifications:Material:304 Stainless steelThread:M6Thread length:35mm/1.37inchHead size:20 x 20 x 4 mm/0.78 x 0.78 x 0.15inchColour:As Pictures Shown