I have a Hawke Vantage and got the sunshade tube & flip up dust caps and I cant get it all together???

The dust caps fit the scope and the sunshade fits the scope but the dust caps wont fit the sunshade. It says on the Hawke website the sunshades are stackable. so if the sunshade screws into the same thread as what the dust caps did and another sunshade will screw into the end of the first then surely so would the dust cap?

I hope that makes sense, Its taken me half an hour to word this as simply as possible!