A slide rail assembly, comprising: a rail member; a first bracket device arranged on the rail member; and a second bracket device detachably mounted on one of the rail member and the first bracket device, wherein the second bracket device is adjustable to displace with respect to the rail member; wherein the slide rail assembly further comprises a first bracket member; wherein the first bracket member is able to be detachably mounted on the one of the rail member and the first bracket device after the second bracket device is detached from the one of the rail member and the first bracket device; wherein the first bracket device and the second bracket device are configured to mount the rail member on a rack of a first type, and the rack of the first type is a four-post rack; wherein the rail member includes a first wall, a second wall, and a longitudinal wall connected between the first wall and the second wall; the first bracket device includes a first sidewall and at least one first mounting member; the first sidewall includes a first portion, a second portion, and a first longitudinal portion arranged between the first portion and the second portion; the first portion, the second portion, and the first longitudinal portion of the first bracket device are respectively adjacent to the first wall, the second wall, and the longitudinal wall of the rail member; the at least one first mounting member is configured to be mounted on a first post of the rack of the first type; the second bracket device includes a second sidewall and at least one second mounting member; the second sidewall includes a third portion, a fourth portion, and a second longitudinal portion arranged between the third portion and the fourth portion; the third portion, the fourth portion, and the second longitudinal portion of the second bracket device define a supporting channel for receiving the first sidewall of the first bracket device; and the at least one second mounting member is configured to be mounted on a second post of the rack of the first type. a rail member; a first bracket device arranged on the rail member; and a second bracket device detachably mounted on one of the rail member and the first bracket device, wherein the second bracket device is adjustable to displace with respect to the rail member; wherein the slide rail assembly further comprises a first bracket member; wherein the first bracket member is able to be detachably mounted on the one of the rail member and the first bracket device after the second bracket device is detached from the one of the rail member and the first bracket device; wherein the first bracket device and the second bracket device are configured to mount the rail member on a rack of a first type, and the rack of the first type is a four-post rack; wherein the rail member includes a first wall, a second wall, and a longitudinal wall connected between the first wall and the second wall; the first bracket device includes a first sidewall and at least one first mounting member; the first sidewall includes a first portion, a second portion, and a first longitudinal portion arranged between the first portion and the second portion; the first portion, the second portion, and the first longitudinal portion of the first bracket device are respectively adjacent to the first wall, the second wall, and the longitudinal wall of the rail member; the at least one first mounting member is configured to be mounted on a first post of the rack of the first type; the second bracket device includes a second sidewall and at least one second mounting member; the second sidewall includes a third portion, a fourth portion, and a second longitudinal portion arranged between the third portion and the fourth portion; the third portion, the fourth portion, and the second longitudinal portion of the second bracket device define a supporting channel for receiving the first sidewall of the first bracket device; and the at least one second mounting member is configured to be mounted on a second post of the rack of the first type.