Outstanding quality, handmade, high tread count tyre, for cyclocross use. 

PPS:

The Puncture Protection System is a special fabric placed between a tire's tread and casing to increase resistance to punctures.
Some tires designed for use on rough roads, cobbles and gravel receive a second layer of PPS between the casing and the inner tube we call PPS2.

Handmade Tires - HCL

Now let's look at what high quality handmade tires from Challenge do to improve you ride. Instead of nylon net, Challenge Handmade tires use high tread count cloth casings made from Polyester (220 to 300 TPI), Corespun cotton (320 TPI) and even Silk (1000+ TPI). These high tread count cloth casings, made on our own looms, have a very thin layer of supple latex applied to their surface to hold the treads together. The resulting casing is 98+% soft, flexible cloth. Two layers of the casing are laid out at a 45 to 50 degree angle (bias) that gives the tire lateral strength and stuctural integrity.