A split-flashing composition for covering a protrusion from a roof, the composition having a flange portion adapted for sealing to a roof surface, the flange portion being substantially planar and having an in-plane spiral shape that describes a closed-loop opening for receiving the protrusion; the flange portion having first and second flange end portions that are connected to each other in-plane and in an off-set manner; a collar portion fixably attached to the flange portion; a closed-loop collar-portion construction having a substantially curved wall section and a substantially planar wall section that are connected to each other and together define an internal volume of space, wherein the substantially curved wall section spirals outwardly from a first substantially curved wall section edge portion to a second substantially curved wall section edge portion; the collar portion having a substantially conical shape, wherein the cross-sectional area of the internal volume of space decreases as the distance between the flange portion and the cross-sectional area increases, the cross-sectional area being in a plane that is substantially perpendicular to a collar-portion longitudinal axis; and the collar portion having a substantially planar wall section that is substantially perpendicular to both a first substantially curved wall section edge portion and a second substantially curved wall section edge portion.