Dimensions for solitary bee tubes?

[JustPotteringAbout]

What range of lengths and internal diameters of tube are suitable for solitary bees to nest and germinate their young in?
(in mm please)
I have a bunch of timber from the skip for for roof and sidewalls, there are mason bees around the garden, probably nested in herbaceous perennial stems and umbelliform weeds I brought from the woods/quarry up the road .

[Kleftiwallah]

Here ya go.

How to Make a Bee Hotel

Cheers, Tony.

[JustPotteringAbout]

Here ya go.

How to Make a Bee Hotel

Cheers, Tony.

Thanks. I made some tubes this afternoon.