Progressive tuning springs, will fit the standard red and the thick silver shocks on FG offroad cars. The rear springs will also fit Hurrax shocks. All springs have an internal diameter because of the manufacturing progress: 21 up to 21,5 mm. Available in several versions: For the front on FG 2WD buggies:y0322/01 - M1, 2,1 x 50 mm, yellowy0322/02 - M2, 2,2 x 50 mm, orangey0322/03 - M4, 2,4 x 50 mm, purpley0322/04 - M5, 2,5 x 50 mm, blueFor the rear on FG buggies, front and rear on FG monster cars and 4WD buggies:y0323/01 - M11, 2,1 x 90 mm, yellowy0323/02 - M12, 2,2 x 90 mm, orangey0323/03 - M13, 2,3 x 90 mm, redy0323/04 - M14, 2,4 x 90 mm, purpley0323/05 - M15, 2,5 x 90 mm, bluey0323/06 - M16, 2,6 x 90 mm, blackFor the front on FG buggies:y0324/01 - M01, 2,1 x 60 mm, yellowy0324/02 - M02, 2,2 x 60 mm, orangey0324/03 - M03, 2,3 x 60 mm, redy0324/04 - M04, 2,4 x 60 mm, purpley0324/05 - M05, 2,5 x 60 mm, bluey0323/06 - M16, 2,6 x 90 mm, blackContents:2 pieces