I used "chat" on website because they say it's the easiest quickest way to contact, Christian C ended up telling me that their measurements are not "standard" that the measurements they use on multiple items, for example "100 gauge" curb chain means different things depending on item number. When I asked why they would use it as a measurement if it's not standard he simply replied "sorry for the inconvenience! YIKES! I'm glad I don't follow through with a $500-1000 chain purchase! When you buy elsewhere 5mm=5mm here god knows what you'll get! Good luck!