What's the format of a reference letter from a former colleague?

[tony87]

Since I can't find my former employer to write a reference letter for me, I can only turn to a former colleague for help.

I know a reference letter from an employe needs to include things like work hours, annual salary, responsibilities, etc. Does a reference letter from a colleague need to include all the things too? I mean, my former colleague didn't work as a personnel officer at the company, so will it sound strange if he gives all kinds of details about my job in the letter?

Thank you! Any help would be appreciated!