OPINION

In these consolidated appeals, Richard Blunt (No. 02-4549) and Carl Green (No. 02-4311) appeal their convictions pursuant to guilty pleas for their involvement in a conspiracy to distribute heroin. Blunt challenges his convictions and twenty-four *32 month sentence for conspiracy to possess with the intent to distribute and to distribute less than 100 grams of heroin in violation of 21 U.S.C. § 841(a)(1), (b)(1)(C) (2000), and 18 U.S.C. § 2 (2000). Green attacks his convictions and 188-month sentence for possession with intent to distribute and distribution of less than 100 grams of heroin, in violation of § 841(a)(1).

Blunt asserts the district court erred in determining his criminal history because he was denied counsel during the course of several prior criminal proceedings that led to convictions attributed to him for sentencing purposes. A defendant who was impermissibly denied counsel in prior criminal proceedings may challenge the use of those earlier convictions to enhance his sentence under the United States Sentencing Guidelines. United States v. Bacon, 94 F.3d 158, 163-64 (4th Cir. 1996).

Blunt concedes the record is silent as to whether he waived his right to counsel as to the convictions in question. As Blunt did not assert this issue at sentencing, he may not raise it on direct appeal because it relies on evidence that is not part of the record. United States v. Russell, 971 F.2d 1098, 1112 (4th Cir. 1992). The appropriate vehicle for such challenges is a motion pursuant to 28 U.S.C. § 2255 (2000).

Green raises two issues on appeal. First he asserts that counsel failed to correct his own inaccurate estimate of Green’s likely sentence following a guilty plea and failed to appropriately explain the gravity of the application of the Sentencing Guidelines to his case. However, the record does not conclusively show that counsel’s representation fell below an objective standard of reasonableness. See United States v. Richardson, 195 F.3d 192, 198 (4th Cir. 1999). Accordingly, we decline to consider this claim on direct appeal as it is better addressed in a post-conviction proceeding commenced under 28 U.S.C. § 2255 (2000).

Green also contends his guilty plea was improperly obtained. Because Green failed to move to withdraw his plea in the district court, we review for plain error. See United States v. Martinez, 277 F.3d 517, 527 (4th Cir. 2002). The record shows that the district court conducted a thorough Fed.R.Crim.P. 11 inquiry; therefore, we find the plea validly entered. See United States v. Puckett, 61 F.3d 1092, 1099 (4th Cir. 1995).

Therefore, we affirm Blunt and Green’s convictions and sentences. We dispense with oral argument because the facts and legal contentions have been adequately presented in the materials before the court.

AFFIRMED.