NiSi Replacement Foam Gasket 3 Pack (Spare Part) is a pack of 3 replacement foam Gaskets for NiSi ND filters.  Foam Gaskets are used to prevent light leaks and stop light from entering between the lens and filter. Foam gaskets are required on all NiSI ND filters and from time to time may need replacing due to wear or damage.  Five sizes of gaskets are available including for ND’s 70x80mm, 75x80mm, 100x100mm, 150x150mm, and 180x180mm.