A kit for containing biological fluid and draining a constituent of the biological fluid, the kit comprising: (A) a cylinder, which has a first static opening to receive the biological fluid； (B) a piston assembly, disposed within the cylinder, comprising a shut-off valve, in which the shut-off valve is configured to form a second mobile opening to receive or drain the constituent when the shut-off valve is fitted to be opened； (C) a removable element that is configured to aspirate the biological fluid through the first static opening, in which the removable element is configured to move the plunger assembly, without being locked in the shut-off valve, such that the first static opening receives the biological fluid； (D) a drain element configured to fit in the shut-off valve, such that the shut-off valve opens and the second mobile opening receives the constituent； and (E) an interaction element, at least a part of which is placed in the cylinder and which is configured to fit in the shut-off valve, such that the shut-off valve opens and the second mobile opening receives a substance and an element of seal that is configured to seal the first static opening when the shut-off valve is opened, in which the interaction element comprises (a) a rod and (b) an adapter element, a part of which is positioned in the rod, which is configured to transport the substance.Un kit para contener fluido biológico y drenar un constituyente del fluido biológico, comprendiendo el kit: (A) un cilindro, que tiene una primera abertura estática para recibir el fluido biológico； (B) un conjunto de émbolo, dispuesto dentro del cilindro, que comprende una válvula de cierre, en el que laválvula de cierre está configurada para formar una segunda abertura móvil para recibir o drenar elconstituyente cuando la válvula de cierre está encajada para ser abierta； (C) un elemento retirable que está configurado para aspirar el fluido biológico a través de la primera aberturaestática, en el que el elemen
