Hello,
You can see the document by typing the service tag of the server on the site here https://dell.to/34LoAjl , and then under "Documentation" there is a "Rack Installation - Sliding Rails" document. Or if you share the DPN number I can check how many cm it is. But I can't find it as 770-BCWN.

For example, when I check for Part #:0PWN3 for 2U, I see as follows
Height (cm)8
Height (cm)8
Length (cm)87
Length (cm)87
Width (cm)13.5
Width (cm)13.5

Hope that helps!

These are the 8N0JT ready rail kit, also known as the A12 rails.  This pdf will give you details:
https://i.dell.com/sites/doccontent/business/solutions/engineering-docs/en/Documents/rail-rack-matrix.pdf

Than you for pdf. There is sizes but I do not clearly understand them. My server is R340 8HDD, no CMA, so by pdf table depth must be 720mm. In fact length or fail is 760mm. Server extend another 30mm in front. As I see in fact server with rails does not fit to 800 mm depth cabinet.

So where to find information about minimum depth of cabinet for server/rails before buying some cabinet?

Hi,
It should probably be taken into account that the dept and internal depth mentioned here are different. For example, 800mm depth cabinet internal depth may not be enough for the server. Unfortunately, I can't help because I don't have any docs. But I think that depth and internal depth lengths should be paid attention to. I don't want to mislead you on this matter, so I will suggest you avoid the problem by contacting your dealer for precise lengths.