An arc tube, comprising: a ceramic wall body defining a discharge chamber therein for enclosing a metal-halide dose having a wall thickness T, the ceramic wall body comprising: a first curved portion and an opposing, second curved portion, wherein a dimension R3 represents a radius of curvature of the first curved portion and the second curved portion; a first conical portion after the first curved portion and a second conical portion after the second curved portion, wherein a dimension L3 represents a length of the first and second conical portions (234A,234B), and wherein a dimension α represents a cone half angle of the first conical portion and of the second conical portion; and a first body-leg transition portion having a first body-leg interface after the first conical portion, and a second body-leg transition portion having a second body-leg interface after the second conical portion, wherein a dimension R4 represents a radius of curvature of the first body-leg transition portion and of the second body-leg transition portion, and wherein a dimension L1 represents the distance between the first body-leg transition portion and the second body-leg transition portion; and wherein the ceramic wall body has a dimension D2 representing a maximum diameter of the ceramic wall body and the following relationships are true: 0.5 < R3/D2 < 1.1 and T/2 < L3 < D2/2 and 1.3 < L1/D2 < 2 and 40° < α < 55°. a ceramic wall body defining a discharge chamber therein for enclosing a metal-halide dose having a wall thickness T, the ceramic wall body comprising: a first curved portion and an opposing, second curved portion, wherein a dimension R3 represents a radius of curvature of the first curved portion and the second curved portion; a first conical portion after the first curved portion and a second conical portion after the second curved portion, wherein a dimension L3 represents a length of the first and second conical portions (234A,234B), and wherein a dimension α represents a cone half angle of the first conical portion and of the second conical portion; and a first body-leg transition portion having a first body-leg interface after the first conical portion, and a second body-leg transition portion having a second body-leg interface after the second conical portion, wherein a dimension R4 represents a radius of curvature of the first body-leg transition portion and of the second body-leg transition portion, and wherein a dimension L1 represents the distance between the first body-leg transition portion and the second body-leg transition portion; and a first curved portion and an opposing, second curved portion, wherein a dimension R3 represents a radius of curvature of the first curved portion and the second curved portion; a first conical portion after the first curved portion and a second conical portion after the second curved portion, wherein a dimension L3 represents a length of the first and second conical portions (234A,234B), and wherein a dimension α represents a cone half angle of the first conical portion and of the second conical portion; and a first body-leg transition portion having a first body-leg interface after the first conical portion, and a second body-leg transition portion having a second body-leg interface after the second conical portion, wherein a dimension R4 represents a radius of curvature of the first body-leg transition portion and of the second body-leg transition portion, and wherein a dimension L1 represents the distance between the first body-leg transition portion and the second body-leg transition portion; and wherein the ceramic wall body has a dimension D2 representing a maximum diameter of the ceramic wall body and the following relationships are true: 0.5 < R3/D2 < 1.1 and T/2 < L3 < D2/2 and 1.3 < L1/D2 < 2 and 40° < α < 55°.