Perdis Cotton appeals the 150-month sentence the district court 1 imposed after granting the government’s Federal Rule of Criminal Procedure 35(b) motion to reduce Cotton’s sentence for his post-sentencing substantial assistance. His counsel has moved to withdraw and filed a brief under Anders v. California, 386 U.S. 738, 87 S.Ct. 1396, 18 L.Ed.2d 493 (1967), arguing that the reduction should have been even greater. Counsel’s argument is unavailing. See United States v. Coppedge, 135 F.3d 598, 599 (8th Cir. 1998) (per curiam) (extent of Rule 35(b) reduction is unreviewable); cf. United States v. Williams, 324 F.3d 1049, 1049-50 (8th Cir. 2003) (per curiam) (refusal to depart further under U.S.S.G. § 5K1.1 is not reviewable unless defendant makes “substantial showing” that court’s decision was based on unconstitutional motive).

Having reviewed the resentencing record under Penson v. Ohio, 488 U.S. 75, 80, 109 S.Ct. 346, 102 L.Ed.2d 300 (1988), we find no nonfrivolous issues. Accordingly, we grant defense counsel’s motion to withdraw, and we affirm.