In order to make a non-overlapping jib as big as possible, it needs battens. Without battens, the leech of the jib would need leach hollow (a concave profile), to keep the back edge of the sail from curling. By adding battens, the leech of the sail can be straight from the head to the clew, or even with some positive roach. In order for the battens to roll up with the sail, they are placed on the sail parallel to the luff. The only drawback to vertical battens is that they need to be more than twice the length of horizontal battens in order to support the leech as well. Longer battens add weight and they are not easy to insert as the sail is being installed on the furler.
Vertical battens on non-overlapping racing jibs simplify mark roundings. The jib can be rolled up with the tug of a furling line as the spinnaker fills; likewise, the jib can be easily unrolled just before the spinnaker comes down. Above: X-Drive Carbon sail on an Arcona 465 Carbon. Below: A Sunfast 3200 with Titanium Blue sails.