These are the variator glide key guides, or Slide for the Chinese GY6, 4T, 139QMB, 50cc variator.

Variator guides (or 'sliders') are the spacers between your variator pulley and the back plate. Regular service of these guides is often overlooked, and may cause excess noise and a loss of performance and acceleration.

Variator guides are a fairly inexpensive component and it makes sense to check them when replacing your roller weights. Sold as a set of three.