20cm
the standard UK size is 520mm long x 110mm wide.
It looks like 68 mm
There isn't a true standard serving platter size. The size of the platter depends on the shape of the platter. A normal rectangular serving tray can range in size from 14x10 inches to 18x12 inches.
The width of a standard American bathtub is between 32 and 42 inches. The size will really depend on what material the tub is made from and whether or not is a wall to wall or a corner tub.
Check the drivers door. There should be a name plate there with the standard tire size for the vehicle.
Wall ovens are uniform in size. The standard sizes are 30 inches wide, 27 inches wide, and 24 inches wide. Wall ovens come in white, black, and stainless.
Canada and US - Standard size breaker in home panel is 40 amps for stove. If not standard range open Discuss Question page.
If you are talking about a typical 4"x4" box, you can use a pair of combination dual switches (they have the same shape as a standard receptacle, so you could use a plate made for a double duplex receptacle...see for the type of switch I had in mind) .
One can purchase a wall plate hanger at a home decorating store. A wall plate hanger can also be found at a store that has a section for home decorations.
Generally for external walls its 90x35 and interiour walls are usually 70x35 unless load bearing
They do with the most predominate sizes being 24", 27" and 30". The size that is widely used is 30".