After a web search and buy 2 bags Tamaris (a city bag and postbag) here are the dimensions of the different models:
Tamaris -the city bag (25 x 9 x 27) the first number is the width
-the Tamaris postbag (27 x 7 x 22) the first number is the width
-the messenger tamarisk (40 x 10 x33)
dimensions can vary a bit of 1 or 2 cm according to my findings