Abstract: The present invention is a thermally conductive sheet comprising: a matrix comprising an organic polymer, and a carbon fiber X, the carbon fiber X being oriented in a thickness direction of the sheet, wherein a proportion of a carbon fiber (A) having a fiber length of 100 µm or less is 40% or more and a proportion of a carbon fiber (B) having a fiber length of 200 µm or more is 3 to 13% of the carbon fiber X. According to the present invention, a thermally conductive sheet in which the thermal resistance value is effectively reduced by polishing the surface, resulting in a sheet having a low thermal resistance value can be provided.

Abstract: A spark plug having a ceramic insulator held by a crimp portion of a metallic shell. The crimp portion satisfies a relation of A?1.7 mm and a relation of t?1.20 mm in a cross section of the crimp portion taken along a plane containing the axial line, where A is the distance between a closest point which is a point within the cross section closest to the ceramic insulator and an intersection at which a first orthogonal line passing through the closest point and orthogonal to the axial line intersects with an outer circumference of the crimp portion, and t is a thickness of the proximal end of the crimp portion.

Abstract: A spark plug having a ceramic insulator held by a crimp portion of a metallic shell. The crimp portion satisfies a relation of A?1.7 mm and a relation of t?1.20 mm in a cross section of the crimp portion taken along a plane containing the axial line, where A is the distance between a closest point which is a point within the cross section closest to the ceramic insulator and an intersection at which a first orthogonal line passing through the closest point and orthogonal to the axial line intersects with an outer circumference of the crimp portion, and t is a thickness of the proximal end of the crimp portion.