This is a replacement ProTek R/C Samurai 321B, RM.1, RM, CR21, S03 & R03 Mid Needle, and is used to regulate the fuel flow in the middle throttle range. This needle also includes one large and one small mid needle o-ring. O-rings available separately (PTK2533 & PKT-2534).
This product was added to our catalog on November 6, 2014