Take This to the Hardware Store
If you don't know the brand of the cat tree or it's not one mentioned here, we'll need to know the thread size of the bolts/studs on your tree. You can determine this easily enough by taking one of the bolts or studs to a hardware store and finding a matching nut. Many Chinese-made cat trees use metric hardware, such as M8 x 1.25, or M10 x 1.5. These numbers refer to the diameter and the pitch, with the first number - such as M8 - being the diameter, and the second number - such as 1.25 - being the pitch. The pitch designations mentioned here are standard pitches for coarse threads in each of their diameters. This would be a good place to start when you go to the hardware store. The Foster/Smith brand uses a non-metric American thread size. In either case ( metric or American thread ), we'll need this to be expressed in this way when you contact us. You'll find any nut or bolt will have these types of specifications on its bin in the store or on its packaging. If you need help, ask someone to make this determination for you.