There has been some discussion over the use of Spectra vs. paracord vs. climbing rope/access. cordage. There are two types of rope used in climbing/rappelling; their internal structure and uses are very different. Both generally made of nylon, the structure in called kern-mantle. There is an outer sheath, whose major function is to protect the inner fiber structure, where the true load bearing function takes place. The inner core for both lead climbing and rappelling is comprised of thousands of nylon fibers that are continuous and run the entire length of the rope. The difference between the construction of lead climbing rope and rappelling/rescue rope lays in the way the nylon fibers are oriented. In lead climbing rope, a climber who maybe climbing above an anchor point may fall, he/she wants the rope to act as a shock absorber, absorbing the energy of the falling climber. The inner core of climbing rope has multiple bundles of spirally twisted nylon fibers, which when place under load will stretch and absorb the weight of the climber. This rope is often referred to as dynamic and can stretch as much as 40%. Rappelling or rescue rope has the internal nylon fibers virtually straight, with no coiling, this rope is sometimes referred to as “static” or more appropriately as low stretch, since it will stretch around 5-8% (depending on manufacturer and other factors). If a 150 lb. climber were to use this rope and fell 10 feet above their last anchor point (total fall of 20 ft.) they would like either break the rope or suffer major injuries. While it is true, Spectra cordage is stronger for the amount of weight when compared to nylon rope; there have been reports that the inner core has a tendency to breakdown and powder with use. I would never use 550 paracord as lifeline. Keep in mind that climbing and /or rappelling rope has a breaking strength in the thousands of pounds. I sorry if this post is long, but there are dozens rescues SAR teams have to make each year, because someone thought rope they were using could hold several hundred pounds and they only weighed 150 lbs. Pete