Gutters & Downpipes. Although Ratio does not have a Builder's range in OO gauge, we have grouped these kits here and have a similar way to the N gauge Builder series to help scratchbuilders. These are all parts from kits that we have made available seperatley to help you add detail to your models. Of course you can use the parts also to extend your kit projects. For example, kits such as the Coal Staithes or Oil Tanks could be combined to make a large fuel storage depot.