ND13 Neutral density filter to fit 1.25" filter threads (13% transmission). The 13% neutral density filter reduces transmission evenly accross the spectrum. The ND13 is a great filter for glare reduction and is very useful when observing the Moon and can be useful for splitting close double stars. The filter is made of top quality optical glass and is mounted in a black anodised aluminium holder and is supplied in plastic storage case.