Posted By Renny Thomson TechSP As far as I can recall there is no specified height, but you would need to check the detail of the Construction & Use Regs to be certain. Your local Vehicle Inspectorate Office should be able to asssist. As far as adjustment is concerned - the restraint should be positioned so that the "bulge" on the back of the skull will be arrested by the restraint. If the restraint is too low the result can be a very sertious neck injury as you are probably aware. The difficult bit is educating drivers and passengers to adjust the restraint to suit themselves. I am fairly conciencious about this, but at over 6 foot, I find some vehicles do not adjust sufficiently and hve deleted some cars off of my desirable list because of this.