A boot comprising: an upper section including an outer shell and an inner lining and absent any attaching devices, one partial length opening section which is located on an inwardly facing portion of said upper section, at a position to expand for an entering or exiting foot, and including a first slit defined as having parallel borders formed within said outer shell and a second slit formed within said inner lining and aligned with said first slit, a material with elastic properties embedded in said opening section between said first slit and said second slit, said material being entirely sandwiched between said outer shell and said inner lining, and a sole; wherein said upper section is further defined by an upper above said sole and with an extended cylindrical portion tapered at the ankle area extending upwardly from said sole and configured to cover at least a portion of the calf area with a generally circular upper edge defining a top opening of said boot at the top of said extended cylindrical portion; wherein said top opening is configured to allow for a wearer to insert a foot; said inwardly facing portion is a medial side; said first and said second slits (300,110) are each located along said medial side and do not directly intersect said generally circular upper edge of said top opening of said boot; and said opening section is fully located within said upper section, is generally in a closed position with said parallel borders directly touching one another which causes said unstretched material to be entirely hidden behind said first slit with said parallel borders when viewing directly from said medial side, said opening section being expandable so as to accommodate said foot entering or exiting said boot, and being automatically self-revertible to said closed position following said foot's entry or exit. an upper section including an outer shell and an inner lining and absent any attaching devices, one partial length opening section which is located on an inwardly facing portion of said upper section, at a position to expand for an entering or exiting foot, and including a first slit defined as having parallel borders formed within said outer shell and a second slit formed within said inner lining and aligned with said first slit, a material with elastic properties embedded in said opening section between said first slit and said second slit, said material being entirely sandwiched between said outer shell and said inner lining, and a sole; wherein said upper section is further defined by an upper above said sole and with an extended cylindrical portion tapered at the ankle area extending upwardly from said sole and configured to cover at least a portion of the calf area with a generally circular upper edge defining a top opening of said boot at the top of said extended cylindrical portion; wherein said top opening is configured to allow for a wearer to insert a foot; said inwardly facing portion is a medial side; said first and said second slits (300,110) are each located along said medial side and do not directly intersect said generally circular upper edge of said top opening of said boot; and said opening section is fully located within said upper section, is generally in a closed position with said parallel borders directly touching one another which causes said unstretched material to be entirely hidden behind said first slit with said parallel borders when viewing directly from said medial side, said opening section being expandable so as to accommodate said foot entering or exiting said boot, and being automatically self-revertible to said closed position following said foot's entry or exit.