Headwear having size adjustment device

Headwear having an opening and a size adjustment device that are formed in a head receiving portion,

• wherein the size adjustment device comprises:
• a first size adjustment member defining a first longitudinal axis;
• a second size adjustment member defining a second longitudinal axis;
• wherein said first longitudinal axis of said first size adjustment member is collinear with said second longitudinal axis of said second size adjustment member;
• wherein at least one of said first size adjustment member and said second size adjustment member define a first size adjustment unit that defines shape change holes, each of the shape change holes having a constant size and a constant shape, said first size adjustment unit disposed at a lower part of the opening adjusting a size by deforming the shape of said shape change holes for establishing an appropriate size for wearing comfort, a second size adjustment unit being connected to the first size adjustment unit to adjust a size to a constant gap;
• wherein said size adjustment of said first size adjustment unit is less than said constant gap size adjustment of said second size adjustment unit;
• and
• wherein the first size adjustment unit has a body having a vertical longitudinal dimension and a horizontal width dimension, said body defining each of the shape change holes and, said body having vertical symmetry, each of the shape change holes having a longitudinal diameter almost corresponding to a width of the body.