What's the back of a watch called?

What's the back of a watch called? The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the cesium freq... 続きをみる

What can I use for lens cleaner?

What can I use for Lens Cleaner? Combine 3 parts rubbing alcohol with 1 part water - we like to pour everything into a small cup so it's easier to st... 続きをみる