Key lengths can be variable, but in general one should use a key length of 8 characters or more, or some key that can be at least 128 bits in length, or greater. Depending on the PKI technique used the key could vary anywhere from 128 bits to 2048 or more.
My house key is 0.95 of 5.8 centimetres.
A key on a computer keyboard.
Keys come in many sizes. I have a travel case key which is only 2 cm long, and an old fashioned 'house door' key which is 12 cm long.
maybe about 2 inches
It is (or should be) given by the key.
35 mililiters it depends on the lenth