Tape, it has been very useful at times and it has been not helpful at times. It can help hold the roller coaster together which is great but if you put tape inside where the marble runs it causes major friction and slows down your marble. Too much energy at the beginning of our roller coaster has cause our marble to fly off countless times but our progress so far is good. One thing that has been really frustrating is one of our teammates has left for summer so it's down to just two of us but it has been cool to work with my friend.