Roof bars for Volkswagen VW CrossPolo - see Polo Dune

Aluminium bars include full length T-track slots for fixing accessories; you can use the whole length of the bar for load carrying. Most aluminium bars are also low noise, low drag.

Steel bars have a shorter load carrying length because the accessories are fixed around the bars, and the roof bar feet get in the way of these fixings.

Through bars stick out beyond the roof bar feet; you will be able to carry more, and space your accessories further apart, than if you use flush bars with closed ends.