"sizeasy" is a terrific free web service, currently in beta testing, which provides a useful tool to allowing you to compare your desired items to everyday goods to help develop a frame of reference for the size of individual items. Please try to utilize this service prior to placing your order.
It's so easy. All you have to do is as follows:
1) Enter the dimensions of your item in the "Size" box and then click the "add" button.
2) Click the "compare to" button to select the item to be compared with your item.
3) You can see comparisons represented by 3D graphics, as below.