Holyrood is a commemorative tartan, designed by Alistair Buchan of Lochcarron of Scotland to commemorate the Silver Jubilee of Queen Elizabeth II in 1977. Like a fashion/universal tartan it is for everbody to wear.
Holyrood is also the name of the royal castle in Edinburgh, the Scottish equivalent of Buckingham Palace.
On the pictures below three different kilts are to see. Two are 3 yard, ligthweight economy kilts and identical except for the length. One is 21", which, depending on how I wear it, shall be either too short or barely acceptable according to norms. The other one is 22". The third Holyrood kilt is a 22.5" 5 yard 11 oz. wool kilt from Heritage of Scotland.