KMC's S1 chain is a 1/2" X 1/8" chain for use with single speed, internally geared and fixie bikes. Anti-Drop design helps reduce the likelihood of dropped chains. Formerly the Z410 model. 

• Speeds:    1sp    
• Size:    1/2x1/8
• Links:    112L    
• Material:    DB
• Width:    8.6mm