I don't know the width of the ski off the top of my head, but I'm fairly sure they are at least 8", I'll check. The kit is $469 w/ the 4" carbide. 6" is $10 more and 9.5" is $20 more (US $).
This is SLP's description of the ski bottoms:
The SLT™ (Straight Line Tracking™) Ski is made of high quality UHMW plastic for a super strong, durable, wear resistant ski that is extremely slippery and remains flexible even in severe cold conditions. Its patented rocker keel design places more forward weight directly below the spindles for increased keel penetration and better bite in the turns. It results in precise, effortless steering in all snow conditions.
Unique Center Keel Design:
Center keel features an hour glass design with a concave front to minimize tracking even on frozen, rutted trails.
Outer Gull Wings:
Outer gull wings reduce darting, increase flotation by trapping and compacting snow underneath the ski, and increase turning ability by providing additional steering component surface area.
Carbide Combinations:
Multiple carbide combinations are available to match individual riding styles and snow conditions.
(PN 35-127 Carbide and PN 35-121 Keel Blade. This combination provides the maximum reduction of darting on groomed or hard-packed trails.)
Straight Line Tracking and SLT are Trademarks of Starting Line Products Inc.,
Ski design Patent #5700020, #6012728, and Patents Pending.