Does it match this one? http://www.amazon.com/Olympic-Chrome-Straight-Training-Collars/dp/B001QV9JTU
The above says 31 pounds / 300 pounds max.
The shorter bar at my gym is 32 pounds - I weighed it on the gym scale.
My understanding is they are supposed to be 15KG (33 pounds) but manufacturers (and scales) vary.