The new SLS Slide and Lock System large is the latest generation ballast system from Mares. The system uses a mechanical interference based system that during insertion pushes the holding prongs into position and prevents them from retracting. During release, it does not only eliminate the interference, but also pulls the prongs inwards via a system of sliding surfaces, ensuring that the male and female buckles can be removed.

Ease of use is ensured by a large handle and a tunnel on the jacket which controls the insertion of the ballast pocket so that the male buckle is aligned with the female. A finger is then used to push the slider in, which is accompanied by a loud "click" but also by the appearance of a green closed padlock in a special window that replaces a red open padlock.
The large pocket has a capacity of 6kg and a heavy duty zip.
The main features of the SLS large ballast system are:
- Robust zipped pocket
- Easy to slide into the pocket
- Visual aid to check that the system is correctly attached
- Avoids unintended release of weight pockets
- Easy to use with thick gloves