A piston for an internal combustion engine, comprising: a piston body extending along a central longitudinal axis; said piston body having an upper wall forming an upper combustion surface and an annular ring belt depending from said upper combustion surface; said upper combustion surface having first and second portions (18, 20), said first portion extending annularly along an outer periphery of said upper wall and said second portion forming a combustion bowl depending radially inwardly from said first portion; said upper wall having an undercrown surface formed on an underside thereof, said undercrown surface located opposite said second portion of said upper combustion surface and radially inwardly of said ring belt; said piston body including a pair of skirt panels depending from said ring belt; said piston body including a pair of pin bosses spaced from one another by said skirt panels and providing a pair of laterally spaced pin bores; said piston body being free of a cooling gallery along said undercrown surface; and said undercrown surface having an exposed 2-dimensional surface area (Au2D), as viewed looking along said central longitudinal axis, ranging from 25 to 60 percent of a cross-sectional area defined by a maximum outer diameter of said piston body, wherein said piston body includes undercrown pockets located radially outwardly of said pin bosses, at least a portion of said undercrown pockets form at least a portion of said undercrown surface, and said undercrown pockets have a total 2-dimentional surface area (Ap2D) ranging from 18 to 35 percent of said cross-sectional area defined by said maximum outer diameter of said piston body, wherein said undercrown surface is located along said underside of said upper wall at a distance away from said upper combustion surface, and said distance is not greater than 10 mm, characterized in that said undercrown surface has a diameter (Du) ranging from 100 to 140 percent of a diameter (Dc) of said combustion bowl. a piston body extending along a central longitudinal axis; said piston body having an upper wall forming an upper combustion surface and an annular ring belt depending from said upper combustion surface; said upper combustion surface having first and second portions (18, 20), said first portion extending annularly along an outer periphery of said upper wall and said second portion forming a combustion bowl depending radially inwardly from said first portion; said upper wall having an undercrown surface formed on an underside thereof, said undercrown surface located opposite said second portion of said upper combustion surface and radially inwardly of said ring belt; said piston body including a pair of skirt panels depending from said ring belt; said piston body including a pair of pin bosses spaced from one another by said skirt panels and providing a pair of laterally spaced pin bores; said piston body being free of a cooling gallery along said undercrown surface; and said undercrown surface having an exposed 2-dimensional surface area (Au2D), as viewed looking along said central longitudinal axis, ranging from 25 to 60 percent of a cross-sectional area defined by a maximum outer diameter of said piston body, wherein said piston body includes undercrown pockets located radially outwardly of said pin bosses, at least a portion of said undercrown pockets form at least a portion of said undercrown surface, and said undercrown pockets have a total 2-dimentional surface area (Ap2D) ranging from 18 to 35 percent of said cross-sectional area defined by said maximum outer diameter of said piston body, wherein said undercrown surface is located along said underside of said upper wall at a distance away from said upper combustion surface, and said distance is not greater than 10 mm, characterized in that said undercrown surface has a diameter (Du) ranging from 100 to 140 percent of a diameter (Dc) of said combustion bowl.