A road vehicle wheel trim system comprising: a trim component (5, 28) for fitment to a road vehicle wheel (1, 21); and a retainer for the trim component; wherein the trim component (5, 28) comprises a male (9, 30) fitting and the retainer is arranged, in use, to be at least partially disposed in a through-hole (7, 27) in the wheel to define a female fitting for engaging with the fitting of the trim component (5, 28); and wherein the retainer comprises a body intended in use to be at least partially disposed in the through-hole (7, 27) in the wheel and to define a female fitting; and a head which is sized to prevent it passing into the through-hole; characterized in that: the male (9, 30) fitting and the female fitting comprise multiple 11 rows of teeth spaced along their lengths for engaging with the other of the two fittings so that the male (9, 30) fitting can be, in use, retained within the female fitting over a range of relative positions of the two fittings; and wherein at least part of the head is arranged to be removable from the retainer to enable the remainder of the retainer, in use, to pass through the through-hole (6, 7, 27); and in that: the retainer is moulded in two halves joined by live hinges, which halves are folded together in use to form a generally cylindrical fitting which is inserted into said cylindrical through-hole in said wheel. a trim component (5, 28) for fitment to a road vehicle wheel (1, 21); and a retainer for the trim component; wherein the trim component (5, 28) comprises a male (9, 30) fitting and the retainer is arranged, in use, to be at least partially disposed in a through-hole (7, 27) in the wheel to define a female fitting for engaging with the fitting of the trim component (5, 28); and wherein the retainer comprises a body intended in use to be at least partially disposed in the through-hole (7, 27) in the wheel and to define a female fitting; and a head which is sized to prevent it passing into the through-hole; and a retainer for the trim component; wherein the trim component (5, 28) comprises a male (9, 30) fitting and the retainer is arranged, in use, to be at least partially disposed in a through-hole (7, 27) in the wheel to define a female fitting for engaging with the fitting of the trim component (5, 28); and wherein the retainer comprises a body intended in use to be at least partially disposed in the through-hole (7, 27) in the wheel and to define a female fitting; and a head which is sized to prevent it passing into the through-hole; characterized in that: the male (9, 30) fitting and the female fitting comprise multiple 11 rows of teeth spaced along their lengths for engaging with the other of the two fittings so that the male (9, 30) fitting can be, in use, retained within the female fitting over a range of relative positions of the two fittings; and wherein at least part of the head is arranged to be removable from the retainer to enable the remainder of the retainer, in use, to pass through the through-hole (6, 7, 27); and in that: the retainer is moulded in two halves joined by live hinges, which halves are folded together in use to form a generally cylindrical fitting which is inserted into said cylindrical through-hole in said wheel. the male (9, 30) fitting and the female fitting comprise multiple 11 rows of teeth spaced along their lengths for engaging with the other of the two fittings so that the male (9, 30) fitting can be, in use, retained within the female fitting over a range of relative positions of the two fittings; and wherein at least part of the head is arranged to be removable from the retainer to enable the remainder of the retainer, in use, to pass through the through-hole (6, 7, 27); and in that: the retainer is moulded in two halves joined by live hinges, which halves are folded together in use to form a generally cylindrical fitting which is inserted into said cylindrical through-hole in said wheel.