POWERLIP Roller. (Yamaha)
PN# PLR-212

POWERLIP Chain Roller. 
Model specific single roller with raised Powerlip. (Not a pair)
For upper location. 

Suitable for all types of riding.
Powerlip design reduces chain drag and side plate wear.
Offset Powerlip allows for adjustment to chain center line.
Friction reducing additives and UV protection to eliminate color fade.
Sealed bearings are ABEC & 9002 ISO rated for superior rolling and long life.
New specific fit hardware is included.
Used by championship winning race teams worldwide.
Made in the USA. 

Fitment From Parts Finder:
YAMAHA (01-19) WR 250F Upper

Also Fits models Below:
YAMAHA (92-24) YZ 125 & 250  upper
YAMAHA (20-24) YZ 125X Upper.
YAMAHA (16-24) YZ 250X Upper.
YAMAHA (98-02) YZ 400F, 426F, WR 400F, 426F Upper
YAMAHA (03-18) WR 450F Upper.
YAMAHA (01-18) YZ 250F Upper
YAMAHA (15-19) YZ 250FX  Upper.
YAMAHA (20-24) YZ 250FX, WR 250F Lower or Upper.
YAMAHA (03-17) YZ 450F Upper.
YAMAHA (19-24) YZ 250F, YZ 450FX, WR 450F Lower or Upper.
YAMAHA (18-24) YZ 450F Lower or Upper