diff --git a/packages/massa-web3/src/experimental/basicElements/operationManager.ts b/packages/massa-web3/src/experimental/basicElements/operationManager.ts
index 7c3873ed..1e988ff0 100644
--- a/packages/massa-web3/src/experimental/basicElements/operationManager.ts
+++ b/packages/massa-web3/src/experimental/basicElements/operationManager.ts
@@ -5,9 +5,7 @@ import { BlockchainClient } from '../client'
 import { Signature } from './signature'
 import varint from 'varint'
 import { FIRST } from '../utils'
-
-// TODO: replace with a U64 helper
-const U64_SIZE_BYTES = 8
+import { U64 } from './serializers'
 
 const PERIOD_TO_LIVE_DEFAULT = 10
 const PERIOD_TO_LIVE_MAX = 100
@@ -103,7 +101,6 @@ export class OperationManager {
    * @returns A byte array representing the serialized operation.
    */
   static serialize(operation: OperationDetails): Uint8Array {
-    // TODO: check that unsigned.encode is equivalent to varint.encode
     const components = [
       unsigned.encode(operation.fee),
       varint.encode(operation.expirePeriod),
@@ -227,7 +224,7 @@ export class OperationManager {
     key: PublicKey
   ): Uint8Array {
     // u64ToBytes is little endian
-    const networkId = new Uint8Array(U64_SIZE_BYTES)
+    const networkId = new Uint8Array(U64.SIZE_BYTE)
     const view = new DataView(networkId.buffer)
     view.setBigUint64(FIRST, chainId, false)
 
diff --git a/packages/massa-web3/src/experimental/basicElements/storage.ts b/packages/massa-web3/src/experimental/basicElements/storage.ts
index f9c4e24e..2abb44f5 100644
--- a/packages/massa-web3/src/experimental/basicElements/storage.ts
+++ b/packages/massa-web3/src/experimental/basicElements/storage.ts
@@ -1,10 +1,8 @@
 import { toNanoMas } from '../utils'
+import { U32 } from './serializers'
 
 const BYTE_COST_MASSA = 0.0001
 
-// TODO: replace with a U32 helper
-const U32_SIZE_BYTES = 4
-
 // TODO: replace by the underlying logic of the storage cost
 const ACCOUNT_SIZE_BYTES = 10
 
@@ -48,5 +46,5 @@ export function smartContract(numberOfBytes: number): bigint {
  * @returns The cost in the smallest unit of the Massa currency.
  */
 export function newEntry(): bigint {
-  return bytes(U32_SIZE_BYTES)
+  return bytes(U32.SIZE_BYTE)
 }