its dont have any specific unit .its only take the value height and width in
int.

It depends on the context.  For Control properties (Size, Bounds,
ClientRectangle, etc), it's pixels.  But for drawing, when the Size is
passed to something operating on a Graphics object, the Size is
interpreted according to the PageUnit property of that Graphics object.
 So it could be any of the units found in the GraphicsUnit enumeration
except World, in that case.

Note of course also that a Graphics can have a transformation applied to
it, so any drawing using a Size is also affected by that.  If the
PageUnit is Pixels, but you've got a 50% scaling factor applied, then
any Size you pass to a Graphics object winds up being in half-pixels
rather than whole pixels.

All the above is true for the Point struct too.

Pete