Composite Insulators for 25 KV line Stay, Bracket and 9Tonnes. Polymeric Insulator combines mechanical strength with excellent pollution-free performance. High tensile strength of glass fibre combined with  HV shedded profile produces rugged, lightweight tension insulators for overhead line applications. Railway Polymeric Insulator combines mechanical strength with excellent pollution performance. High tensile strength of the glass fibre combined with HV shedded profile, makes it a rugged and lightweight tension insulator for overhead line applications.