I Bought this type of trim to test it out in a new house I bought. It is not composite or any wood based substance, it is basically plastic. Very brittle, cracks very easily. You must use a saw blade with very fine teeth or it will splinter when you cut it. In the end I wish I would have found some wood or composite trim to use. Check out these reviews, they explain the same thing for this quarter round stuff made of the same plastic:

http://www.homedepot.com/p/Timbron-14-ft-x-3-4-in-x-7-16-in-127T-White-Solid-Extruded-Plastic-Base-Shoe-Moulding-127-TLF/203124127