For Distribution panel applications the ST Series is the unit of choice. With the Enhanced Transient Filter (ETF) the ST Series assures that all downstream equipment is receiving clean power. The wide variety of strengths and fusing options makes this ST Series series the most versatile line of surge suppression on the market. The distribution panel suppressor is the second stage of lightning protection and protects downstream equipment from internal transients generated by equipment in other areas of the facility. For space restricted or recessed panels, use LowProfile ETF units.