An elevator system (1, 1', 201, 201'), comprising: an elevator car (10, 10', 210, 210'); an elevator counterweight (2, 2', 2", 2′′′, 202, 202'), comprising: a first part (4, 4', 4", 4′′′, 204, 204') configured to be connected, in use, to a suspension member (8, 8', 208, 208') of an elevator system (1, 1', 201, 201'), wherein the first part (4, 4', 4", 4"', 204, 204') is arranged to receive an additional mass (6, 6', 6", 6"', 206, 206') when the first part (4, 4', 4", 4′′′, 204, 204') is connected to the suspension member (8, 8', 208, 208'), such that a mass of the elevator counterweight (2, 2', 2", 2"', 202, 202') can be varied; a mass variation system (12, 12', 212, 212'), wherein the mass variation system (12, 12', 212, 212') is arranged to add the additional mass (6, 6', 6", 6′′′, 206, 206') to the first part (4, 4', 4", 4′′′, 204, 204') and/or remove the additional mass (6, 6', 6", 6"', 206, 206') from the first part (4, 4', 4", 4"', 204, 204'), so that the mass of the elevator counterweight (2, 2', 2", 2"', 202, 202') can be varied; and characterised by comprising at least one of: a dynamic display (20, 20', 220, 220'), wherein the dynamic display (20, 20', 220, 220') is arranged to display a current duty load, wherein the current duty load varies in correspondence with variation in the mass of the elevator counterweight (2, 2', 2", 2"', 202, 202'); and/or at least one operation-mode display (20, 20', 22'), wherein the operation-mode display (20, 20', 22') is arranged to display an indication of an elevator mode of operation, wherein the mode of operation corresponds to a variation in the mass of the elevator counterweight (2, 2', 2", 2′′′, 202, 202'). an elevator car (10, 10', 210, 210'); an elevator counterweight (2, 2', 2", 2′′′, 202, 202'), comprising: a first part (4, 4', 4", 4′′′, 204, 204') configured to be connected, in use, to a suspension member (8, 8', 208, 208') of an elevator system (1, 1', 201, 201'), wherein the first part (4, 4', 4", 4"', 204, 204') is arranged to receive an additional mass (6, 6', 6", 6"', 206, 206') when the first part (4, 4', 4", 4′′′, 204, 204') is connected to the suspension member (8, 8', 208, 208'), such that a mass of the elevator counterweight (2, 2', 2", 2"', 202, 202') can be varied; a mass variation system (12, 12', 212, 212'), wherein the mass variation system (12, 12', 212, 212') is arranged to add the additional mass (6, 6', 6", 6′′′, 206, 206') to the first part (4, 4', 4", 4′′′, 204, 204') and/or remove the additional mass (6, 6', 6", 6"', 206, 206') from the first part (4, 4', 4", 4"', 204, 204'), so that the mass of the elevator counterweight (2, 2', 2", 2"', 202, 202') can be varied; and characterised by comprising at least one of: a dynamic display (20, 20', 220, 220'), wherein the dynamic display (20, 20', 220, 220') is arranged to display a current duty load, wherein the current duty load varies in correspondence with variation in the mass of the elevator counterweight (2, 2', 2", 2"', 202, 202'); and/or at least one operation-mode display (20, 20', 22'), wherein the operation-mode display (20, 20', 22') is arranged to display an indication of an elevator mode of operation, wherein the mode of operation corresponds to a variation in the mass of the elevator counterweight (2, 2', 2", 2′′′, 202, 202'). a first part (4, 4', 4", 4′′′, 204, 204') configured to be connected, in use, to a suspension member (8, 8', 208, 208') of an elevator system (1, 1', 201, 201'), wherein the first part (4, 4', 4", 4"', 204, 204') is arranged to receive an additional mass (6, 6', 6", 6"', 206, 206') when the first part (4, 4', 4", 4′′′, 204, 204') is connected to the suspension member (8, 8', 208, 208'), such that a mass of the elevator counterweight (2, 2', 2", 2"', 202, 202') can be varied; a mass variation system (12, 12', 212, 212'), wherein the mass variation system (12, 12', 212, 212') is arranged to add the additional mass (6, 6', 6", 6′′′, 206, 206') to the first part (4, 4', 4", 4′′′, 204, 204') and/or remove the additional mass (6, 6', 6", 6"', 206, 206') from the first part (4, 4', 4", 4"', 204, 204'), so that the mass of the elevator counterweight (2, 2', 2", 2"', 202, 202') can be varied; and characterised by comprising at least one of: a dynamic display (20, 20', 220, 220'), wherein the dynamic display (20, 20', 220, 220') is arranged to display a current duty load, wherein the current duty load varies in correspondence with variation in the mass of the elevator counterweight (2, 2', 2", 2"', 202, 202'); and/or at least one operation-mode display (20, 20', 22'), wherein the operation-mode display (20, 20', 22') is arranged to display an indication of an elevator mode of operation, wherein the mode of operation corresponds to a variation in the mass of the elevator counterweight (2, 2', 2", 2′′′, 202, 202'). a dynamic display (20, 20', 220, 220'), wherein the dynamic display (20, 20', 220, 220') is arranged to display a current duty load, wherein the current duty load varies in correspondence with variation in the mass of the elevator counterweight (2, 2', 2", 2"', 202, 202'); and/or at least one operation-mode display (20, 20', 22'), wherein the operation-mode display (20, 20', 22') is arranged to display an indication of an elevator mode of operation, wherein the mode of operation corresponds to a variation in the mass of the elevator counterweight (2, 2', 2", 2′′′, 202, 202').