Carradice SQR tour. Carry up to 22 lbs. (
Length 37cm, Width 18cm, Depth 20cm) I use it on my road bike when I commute. I can put quite a lot of stuff in their (mostly clothes - rain gear... not heavy, but they can take up space.) I throw my extra tube, Co2, patch kit tire levers in their already in a separate saddle bag. I also have a Lezyne micro floor drive pump that fits in their just fine:
My road bike is a cannondale synapse carbon fiber... I think it's the bike I would ride on anything up to 400K.