It is a dual throttle cable set up (see photo below) and should be same as our Rockets. As they specifically listed it for the Rocket if it doesn't fit just get a refund though eBay as an incorrect listing. Triumphs are metric like *** bikes and Rockets have 1" bars so it should be fine.
Often folks have to remove/cut out the plastic cable nipple holder tube from their stock grips to fit aftermarket grips anyway as they often do not come with the throttle cable tube. Do NOT cut the end off your stock one you need the tube underneath the grip rubber as well. Also do NOT do it until you know it is needed and then just slash the grip rubber and peel off.