When our customers order spare barrels for their ZOOM Double Barrel trimmer, we always ask which barrel they would like to purchase - a Left Barrel or a Right Barrel, or a set of Barrels. There is a reason behind.
The Left Barrel and Right Barrel are perforated. The perforations form a rifled helical pattern, with the perforation rifling mirrored, one Barrel relative to the other. The Barrel perforation rifling is mirrored because the Barrels counter-rotate, which requires that the rifling be mirrored in order to encourage movement of the plant material down the Barrels when the Barrels rotate.
This design is also patented.