Shun Crank Arms w/ 42t Ring & Double Guard - 170mm - Black 1-1/4" S5/S6 The KMC S1 is a

The KMC S1 is a single-speed chain suitable for use with any single speed drivetrain such as BMX

This is visible in the photos

8mm outer diameter

When it came to designing an all-new hubset focused at trail/transition riders

Style: Flangeless

Shun Crank Arms w/ 42t Ring & Double Guard - 170mm - Black 1-1/4" S5/S6 The KMC S1 is a*READ FULL DESCRIPTION This is a set of 170mm crank arms with 42t double guarded chainwheel. The arms (one left and one right) are forged steel, the chainwheel is steel and the guards are plastic. The Chainwheel is designed for 1 2x3 32 multi speed chains. The arms fit standard JIS square taper spindles. Does not include bottom bracket or spindle bolts nuts.