This accessory set includes almost everything required to be used with Air Track (B8H25339). This set consists of the following parts including the magnets useful for precision collision & non-collision study; these give better results than hook and loop attachment and spring set.Bolt & Wing Nuts x 10Spring Attachments x 4Springs x 4Hook & Loop Attachment Pairs x 2 PairPulley x 1String x 2Slotted Mass & Hanger: Weights 5 g - 4 pcs. & Hanger 5 g x 1Photogate Flags x 8Photogate Arms x 2Launching Cradle x 1Assorted Masses x 8Risers x 8Rubber Bands x 2Hook for Spring x 1Pins x 4