Purchasing at a local hardware store, or at the big box building supply outlet is always tough. If the item is available, usually the price is out of line. If not available, even though it may be ordered, it is usually delayed by shipping.
I don't know how Amazon does it, but shipping, even standard shipping is always prompt, and the description and images make buying the right product a snap.
As far as how it works, have to wait till the house burns down! Siemens is a leader in quality and performance.