I have the 16 Apex le xtx, the sled had ST's on the stock tuners but still pushed in the corners but some more suspension tuning may have fixed that, and also I found the 5" tuners had no floatation at all for the heavy front end of the Apex, so I moved to the 7" VK pro skis with the single deep keel and put ST's on them, these skis have a higher bend at the back of the ski which I find better when backing, I am very happy with this ski combo set up works very well in all conditions on the trail or off trail, I believe the tuners with ST's had a blade on each keel on the ski and I found mud or rocks or even chunks of ice would jam between the keels some times especially later in the season when conditions were softening up abit. hope this helps.