Below Big Bag sewing machines (Union Special, Newlong and CowBoy) are interchangeable, only for reference when order spare parts:
Newlong DN-2HS = CowBoy DN-2HS 
Newlong DN-2W = CowBoy DN-2W 
Newlong DKN-1 = Union Special 51100R 
Newlong DKN-1BP = Union Special 51100BP 
Newlong DKN-3BP = Union Special 56100MZ27B 
Newlong DKN-3W = Union Special 56500JZ62BN 
Newlong DR-3A = Union Special 80200A 
Newlong HR-2A = Union Special 81200A = CowBoy 81200A 
Newlong DD-5 = CowBoy 7133 
Newlong DHR-6 = Union Special 81300A = CowBoy 81300A 
Newlong DR-7UW = Union Special 80700CD = CowBoy 80700CD

Web Sling Vs. Synthetic Sling

Web Sling Vs. Synthetic Sling

 In rock climbing, your gear is what keeps you alive when you fall. With this in mind, it is important to choose the proper tools for each unique climbing situation. 
Webbing, sewn runners and slings made of synthetic materials like Dyneema or Spectra have multiple uses in the vertical world. 
Building Anchors Slings made of knotted, tubular nylon webbing and slings made of other synthetic materials like Dyneema or Spectra may all be used to build anchor systems for rappelling or belaying another climber. All are strong materials that, when used properly, will support a climber's weight. Tubular webbing, which is often bought in bulk, will need to be cut and tied off to form slings. Slings made from other synthetic materials come pre-sewn in different lengths. Different materials offer comparable strength, but slings made of tubular webbing can be made before the climb to any dimensions the climber prefers. 

Climbing Protection Both tubular webbing and synthetic, sewn runners are used to protect in dangerous sections of climbing. Slings may be draped around rock protrusions, threaded through holes in rocks and tied off around trees or stone knobs to catch a climber if he slips and falls. Again both slings made of bulk webbing and sewn synthetic slings are used in these situations. If using homemade knotted slings of tubular webbing (the cheaper option, as it can be purchased in bulk) make sure to tie proper knots and leave long tails on either side of the knot to prevent slippage. Preventing Rope Drag On long climbs, friction from the rope passing through many carabiners placed as pieces of protection becomes an aggravating force. 

On routes that wander across the face of a cliff, rope drag can become unbearable. Slings, made of either webbing, Dyneema or Spectra, reduce rope drag when clipped into pieces of protection and the climber's rope by extending the points of protection, allowing the rope to flow upward behind the climber in as straight a line as possible. When using either knotted webbing or synthetic slings, inspect your gear before and after each climb to make sure it is in working order. Replace any slings that show signs of fraying or wear.

As Direct Protection Both knotted webbing slings and synthetic sewn slings are used by climbers to as direct protection. The climber, when ready to take a rest, clips two slings that are attached to the belay loop of his harness into a bolt or anchor system in place in the rock using carabiners. 

The climber may now put his weigh on the slings allowing his belayer to relax a bit and tend to other issues. As in any situation trusting your life to a piece of gear, make sure the slings are in good shape and, if using knotted webbing, that the knots are secure and have long tails to prevent slipping.