It's sized just right, at 1L its neither too small or too large. If it was bigger it might be too heavy, smaller and there wouldn't be enough Yerba Maté/coffee. 
 
This thermos has no glass on the inside (which breaks when you drop it) but is fully stainless steel inside and out. Two screwable lids makes for a bigger hole when refilling.
No more drips with this fantastic, well designed pouring spout; developed to stop water immediately when tilting back after pouring. 
Thermos can also be used for other beverages like tea or coffee as it comes with a cap designed as a cup.