Abstract: In each of radial grooves 52 which are formed on a sealing disc portion 34 of a packing 10, low strength portions 64 are formed within a predetermined range from the center of the sealing disc portion 34 by decreasing the thickness of each of thin portions 62 by deeply cutting each of the radial grooves 52. When the center of the sealing disc portion 34 is pressed by the pressing means, splits are formed at the low strength portions 64, and extend to curved grooves 54 and circumferential grooves 56. As a result, it is possible to obtain a plugging member in which a draining port can be opened wide with a small amount of pressing force.

Abstract: In each of radial grooves 52 which are formed on a sealing disc portion 34 of a packing 10, low strength portions 64 are formed within a predetermined range from the center of the sealing disc portion 34 by decreasing the thickness of each of thin portions 62 by deeply cutting each of the radial grooves 52. When the center of the sealing disc portion 34 is pressed by the pressing means, splits are formed at the low strength portions 64, and extend to curved grooves 54 and circumferential grooves 56. As a result, it is possible to obtain a plugging member in which a draining port can be opened wide with a small amount of pressing force.

Abstract: In each of radial grooves 52 which are formed on a sealing disc portion 34 of a packing 10, low strength portions 64 are formed within a predetermined range from the center of the sealing disc portion 34 by decreasing the thickness of each of thin portions 62by deeply cutting each of the radial grooves 52. When the center of the sealing disc portion 34 is pressed by the pressing means, splits are formed at the low strength portions 64, and extend to curved grooves 54 and circumferential grooves 56. As a result, it is possible to obtain a plugging member in which a draining port can be opened wide with a small amount of pressing force.

Abstract: A plastic container comprising a bottom portion which has a substantially rectangular bottom surface, a trunk portion which is formed by four planes which rise up vertically from respective sides of the bottom surface and which is substantially rectangular pipe-shaped, a mouth portion whose surface area of a portion surrounded by a horizontal cross section is smaller than the surface area of the trunk portion, and a shoulder portion which is narrowed down from the trunk portion to the mouth portion, characterized in that: the amount of the contents of the plastic container is 800 to 3000 ml; the average thickness of the trunk portion is 0.2 to 0.

Abstract: A plastic container comprising a bottom portion which has a substantially rectangular bottom surface, a trunk portion which is formed by four planes which rise up vertically from respective sides of the bottom surface and which is substantially rectangular pipeshaped, a mouth portion whose surface area of a portion surrounded by a horizontal cross section is smaller than the surface area of the trunk portion, and a shoulder portion which is narrowed down from the trunk portion to the mouth portion, characterized in that: the amount of the contents of the plastic container is 800 to 3000 ml; the average thickness of the trunk portion is 0.2 to 0.