Drop in is sections of 'dendex' dry slope material, which we 'borrowed' from the local dry slope. Its pretty slidey, especially when you put some water on it. Im gonna make the drop in bigger though because you don't get as much speed as i want. The drop in tower is just a load of pallets nailed together, works well, fairly sturdy.
Rail is made of 1.5in diameter piping which i fund in a nearby field, ha...seems to be strong enough