Trail Riding/Packed Snow (for SLT Ski only): Best trail runner combination is the use of SL4-127 Carbide Runner in conjunction with the SLB-121 Keel Blade. This combination, along with the SLT Ski design, achieves the maximum reduction of tracking and darting, with minimal arm effort. Hardweld Runners: For loose snow conditions, these hardweld runners provide good performance. Not recommended when ice may be encountered, especially in corners. Limited control will be available when used in icy conditions. A popular choice for mountain customers who seldom ride the trail. To provide good service life, hardweld area is 13-1/2 long on these runners. Cannot be used with the SLB-121 keel blade. Aggressive Trail / Loose Snow / Mountain Riding: Best carbide runners for aggressive trail and loose snow conditions. 75° carbide for long life, 60° for those who prefer a steeper more aggressive angle. Cannot be used with the SLB-121 keel blade.