This is a nice Type 2 Surge Arrester. The version that I bought is a 30 amp breaker and is used to drive a 220 welder outlet next to my box in the garage. It takes 70KA surges which is a huge hit- the very largest credible hit is probably 100KA but wouldn't happen in my suburban neighborhood. What this rating means in practice is that it will take a large number of small surges before it fails. Many suppressors go dark after one lightning storm- 20KA or so isn't unusual. The picture is a bit deceiving- it is about 2 inches longer than a standard block breaker as pictured. Its compatible and in a standard (large) 200A box but might not in a smaller sub-panel. Overall its an excellent value at about $100.