The maximum weight capacity for our cargo boxes is 165 lbs, but this varies depending on the vehicle, the actual weight maybe less for your vehicle, please see this article regarding how to determine maximum weight capacity.
As to how much stuff can fit, the graphic below is to help visualize the size of the box in relation to skis and snow boards. Also please see the attached PDF that has the full internal and external box dimensions.
If you have further questions please contact us here, or by phone at 888-925-4621 during business hours.