They allow more adjustment than the standard bolts but the main advantage I suppose is they work out cheaper than replacing the 4 with OEM bolts from Nissan
Dealers like Evans Halshaw really are the pits, they were the local Nissan dealer up here but they didn't last long! Best to find yourself a good independent
We keep all service items in stock, most independents will be happy to carry out a service with you supplying the parts, drop me a PM if I can help
Ewen