The Register of Scottish Tartans classifies it as a clan/family tartan.
The kilt is a 5.3 yard ready-made kilt by O'Neil of Dublin. Pure worsted wool, lightweigt. O'Neil of Dublin no longer sells the kilt in this beautiful tartan. But with Scotweb you can have a 5 yard kilt made to order in this tartan for less than £200, it seems.