Hi, This is a post in the context of project performance: If you use loops with feature definitions, take care where you declare ("create") your participating objects: Most of the times, objects can be declared outside of the loop since the dependency is kept within the loop by means of the expression mechanism! In the attached example, I create N curves in between of two given rail curves and store them in a list for surface creation. The two points on the corresponding rails are declared right before the loop starts. You could also declare them within the loop but - and here comes the message - they would be created again and again, i.e. at each iteration (N-times). In the end, this might slow down your feature execution when it comes to a higher number of objects that get declared within a loop. Hope this helps ... Cheers Joerg loop.fdb