8.05mm OD x 6.56mm ID x 200mm 

8.05mm OD x 6.56mm ID x 300mm 

10mm OD x 8.1mm IDx x 400mm 

The 8.05mm OD tube telescopes inside of the 10mm OD tube nicely. 

The 8mm tube is super strong 7075 T6 Aluminum, black anodized

The 10mm tube is 6000 series aluminum, also black anodized. 

The 8mm tube fits over 1/4" threaded rod perfectly and can be used for altimeter sled spacers, or as part of a custom sled solution.