Two types of gobo retention spring are used in the MAC 250 and MAC 250+. Metal gobos are held in place with P/N 17760190, "Gobo Spring, 4 bends, MAC250". All 3 glass gobos in the MAC 250+ and the Fibroid gobo in the MAC 250 are held with P/N 17760250, "Spring for MAC 250-size gobos, 2 bends." P/N 17760250 is also used in the MiniMAC Profile.
Either spring will hold glass or metal gobos. The 4-bend spring is easier to remove. The 2-bend spring has a lower profile and is used with the glass gobos, which are thicker, to increase the clearance from the focus lens in the MAC 250+.