This "economy" spanner set includes just about all the sizes you will ever need on a model heli. Metric Sizes : Closed end : 11, 10, 9, 8, 7, 6, 6, 5.5, 4.5, 4mm Open end:10, 9, 8, 7, 6, 5.5, 5, 5, 4,4.5mm