Racing Sheet Pro has a double-braid construction with a 12-strand core of blended, color-matched SK75 Dyneema and Nylon fiber (50% of each). The cover is a blend of 12-strand Dyneema and Taslan (50% of each material).
This line has lower elongation properties than standard Racing Sheet and maintains its shape very well in clutches. It can be used as a halyard as well as for main and jib sheets.
This line can be stripped of its cover to save weight, while maintaining good gripping characteristics in cleats and clutches.
Abrasion resistant, good grip, with excellent low-stretch performance.
Heavy on the technical side...
Dynema® is the Dutch company DSM Dyneema's brand of UHMWPE (Ultra High Molecular Weight PolyEthylene fiber), a long chain, high strength, oriented strand, synthetic fiber with very high strength as well as high abrasion resistance.
This fiber is also known as HMPE (High Modulus PolyEthylene).
Dyneema is available in a number of formulations, SK-60, SK-75, SK-78, SK-90, etc. Each progressively stronger and more expensive.
Of particular interest these days is the difference between Dyneema SK75 and SK78. Dyneema SK78 has the same high strength of SK75, but with lower creep (non-recoverable stretch).
Honeywell International produces a similar UHMWPE fiber, marketed as Spectra®