Ang, there really is no way to judge such a thing. Bryce's render report wouldn't, for example, say how many bounces a particular object in the scene used... Or an average, or anything like that. But consider that this glass object is an actual Rhino object I modeled. It has an inside and an outside face. So, if you shot a ray straight at it from a perpendicular angle, it would need 1, 2 (for the first side) then 3 and 4 counts to emerge from the other side. And every angle of incidence that is NOT 90 degrees dead on, would need progressively more Depth to let the ray emerge. For example, a light ray going almost straight down along an edge? The more Ray Depth, the merrier! Considering that this model is fairly high-polygon, and smooth, I'm thinking that 18 is probably as high as necessary, although mathematically 16 would make more sense...