The fsa os 99 carbon stem falls under fsas top end k force series this series features the latest advancement in carbon composite and metal alloy technology coupled with state of the art manufacturing processes k force components will always showcase the embodiment of what fsas dedication to advancements in the art of product development the os 99 stem uses both alloy and carbon technologies as it 3d forged and cnc machined from al2014 a lightweight but strong aluminium alloy then fsa app