1) optical glass (borosilicate) material 2) above 94% light transmittance 3 ... resistance 4)clear solar concentrator glass lens(GT-D22-10-1)1)material: optical glass(borosilicate),K9,BK7,B2702) light transmittance: ... , no mould markd,no inside bubble and dirtsb: can match up all kinds of different high power led ,uniform facula ... ,astronomical instrument. solar concentrator glass lens(GT-D22-10-1)