A cap for a container with a threaded neck, comprising: - a cap body having a substantially tubular skirt centered on a longitudinal axis (X-X') and means for engaging with the neck of the container, the cap body being pivotably mounted between a closed position in which the cap body closes off an opening of the neck and an open position in which the cap body is disengaged from the opening of the neck in order to allow access to the inside of the container; - a tamper-evident band centered on the longitudinal axis (X-X') and comprising means for engaging with a collar of the neck; and - two connection arms extending in an angular direction, the connection arms being connected to the tamper-evident band and to the cap body; the cap comprising a locking member positioned between the two connection arms; the locking member comprising a first portion located at the cap body and a second portion located at the tamper-evident band, the first and second portions consisting of solid material; and the first portion and the second portion of the locking member interacting with each other via a bearing connection in order to allow the cap body to be held in a fully open position in which the cap body is fully disengaged from the opening of the neck, the first portion of the locking member consisting of an outwardly projecting lug, the lug having an outer edge; characterized in that: - the second portion of the locking member consists of a block of solid material connected on both sides to the two connection arms, the block comprising an upper end which forms an arc of a circle; and - the second portion comprises a groove provided in the vicinity of the upper end of the block, said groove forming both a bearing point on which the outer edge of the lug bears, and a means for retaining the lug when the cap body is in the fully open position. - a cap body having a substantially tubular skirt centered on a longitudinal axis (X-X') and means for engaging with the neck of the container, the cap body being pivotably mounted between a closed position in which the cap body closes off an opening of the neck and an open position in which the cap body is disengaged from the opening of the neck in order to allow access to the inside of the container; - a tamper-evident band centered on the longitudinal axis (X-X') and comprising means for engaging with a collar of the neck; and - two connection arms extending in an angular direction, the connection arms being connected to the tamper-evident band and to the cap body; the cap comprising a locking member positioned between the two connection arms; the locking member comprising a first portion located at the cap body and a second portion located at the tamper-evident band, the first and second portions consisting of solid material; and the first portion and the second portion of the locking member interacting with each other via a bearing connection in order to allow the cap body to be held in a fully open position in which the cap body is fully disengaged from the opening of the neck, the first portion of the locking member consisting of an outwardly projecting lug, the lug having an outer edge; characterized in that: - the second portion of the locking member consists of a block of solid material connected on both sides to the two connection arms, the block comprising an upper end which forms an arc of a circle; and - the second portion comprises a groove provided in the vicinity of the upper end of the block, said groove forming both a bearing point on which the outer edge of the lug bears, and a means for retaining the lug when the cap body is in the fully open position. - the second portion of the locking member consists of a block of solid material connected on both sides to the two connection arms, the block comprising an upper end which forms an arc of a circle; and - the second portion comprises a groove provided in the vicinity of the upper end of the block, said groove forming both a bearing point on which the outer edge of the lug bears, and a means for retaining the lug when the cap body is in the fully open position.