Very very poor . I bought a stop start battery last year with a 4 year warranty. It failed the other month. I returned the duff battery to the gsf branch in boldon where they discharge tested it proving that it was indeed at fault. I was told that they would send it back to head office and to expect a refund through the warranty. But I have had nothing into my account. I have since spoke with the branch at boldon who supplied me with the customer service number to call. It just rings and rings. I have tried other numbers which do the same. Also I have emailed gsf. Would you believe haven't heard a thing. Disheartened that such a big company gsf is so poor