Due to the UK being shut off from the European mainland because of the new Covid-19 mutation it is very likely your order will be delayed until further notice. There is nothing we can do about this at this point in time
Ski carriers differ from ski boxes because they are purely aimed at the safe transport of skis and snowboards. There is no room for other things. Depending on the width, there may be more or fewer skis. The different rack carriers indicate which roof rack they fit to. In the case of a Thule ski carrier, you can see in the Thule Buying Guide which parts are still needed for a secure fastening on the car.