diff --git a/dagger/blocktype.nim b/dagger/blocktype.nim
index 6cf0c240..87d3b8e1 100644
--- a/dagger/blocktype.nim
+++ b/dagger/blocktype.nim
@@ -16,6 +16,9 @@ import pkg/questionable/results
 
 import ./errors
 
+const
+  BlockSize* = 4096 # file chunk read size
+
 type
   Block* = object of RootObj
     cid*: Cid
diff --git a/dagger/manifest/coders.nim b/dagger/manifest/coders.nim
index 8acd1b70..1a3413b8 100644
--- a/dagger/manifest/coders.nim
+++ b/dagger/manifest/coders.nim
@@ -27,20 +27,20 @@ type
   ManifestCoderType*[codec: static MultiCodec] = object
   DagPBCoder* = ManifestCoderType[multiCodec("dag-pb")]
 
-func encode*(_: DagPBCoder, b: Manifest): ?!seq[byte] =
+func encode*(_: DagPBCoder, manifest: Manifest): ?!seq[byte] =
   ## Encode the manifest into a ``ManifestCodec``
   ## multicodec container (Dag-pb) for now
   ##
 
   var pbNode = initProtoBuffer()
 
-  for c in b.blocks:
+  for c in manifest.blocks:
     var pbLink = initProtoBuffer()
     pbLink.write(1, c.data.buffer) # write Cid links
     pbLink.finish()
     pbNode.write(2, pbLink)
 
-  let cid = !b.rootHash
+  let cid = !manifest.rootHash
   pbNode.write(1, cid.data.buffer) # set the rootHash Cid as the data field
   pbNode.finish()
 
diff --git a/dagger/manifest/manifest.nim b/dagger/manifest/manifest.nim
index 0c1d007e..8e6df348 100644
--- a/dagger/manifest/manifest.nim
+++ b/dagger/manifest/manifest.nim
@@ -19,6 +19,7 @@ import pkg/chronicles
 import ./types
 import ./coders
 import ../errors
+import ../blocktype
 
 export coders, Manifest
 
@@ -30,16 +31,21 @@ const
 func len*(self: Manifest): int =
   self.blocks.len
 
+func size*(self: Manifest): int =
+  self.blocks.len * self.blockSize
+
 func `[]`*(self: Manifest, i: Natural): Cid =
   self.blocks[i]
 
 func `[]=`*(self: var Manifest, i: Natural, item: Cid) =
+  self.rootHash = Cid.none
   self.blocks[i] = item
 
 func `[]`*(self: Manifest, i: BackwardsIndex): Cid =
   self.blocks[self.len - i.int]
 
 func `[]=`*(self: var Manifest, i: BackwardsIndex, item: Cid) =
+  self.rootHash = Cid.none
   self.blocks[self.len - i.int] = item
 
 proc add*(self: var Manifest, cid: Cid) =
@@ -61,6 +67,10 @@ template hashBytes(mh: MultiHash): seq[byte] =
   mh.data.buffer[mh.dpos..(mh.dpos + mh.size - 1)]
 
 proc makeRoot(self: var Manifest): ?!void =
+  ## Create a tree hash root of the contained
+  ## block hashes
+  ##
+
   var
     stack: seq[MultiHash]
 
@@ -119,7 +129,8 @@ proc init*(
   blocks: openArray[Cid] = [],
   version = CIDv1,
   hcodec = multiCodec("sha2-256"),
-  codec = multiCodec("raw")): ?!T =
+  codec = multiCodec("raw"),
+  blockSize = BlockSize): ?!T =
   ## Create a manifest using array of `Cid`s
   ##
 
@@ -131,4 +142,5 @@ proc init*(
     version: version,
     codec: codec,
     hcodec: hcodec,
+    blockSize: blockSize
     ).success
diff --git a/dagger/manifest/types.nim b/dagger/manifest/types.nim
index d1197123..233e3fa5 100644
--- a/dagger/manifest/types.nim
+++ b/dagger/manifest/types.nim
@@ -40,6 +40,7 @@ template EmptyDigests*: untyped =
 type
   Manifest* = object of RootObj
     rootHash*: ?Cid
+    blockSize*: int
     blocks*: seq[Cid]
     version*: CidVersion
     hcodec*: MultiCodec
diff --git a/dagger/node.nim b/dagger/node.nim
index b31fdfab..13d0c876 100644
--- a/dagger/node.nim
+++ b/dagger/node.nim
@@ -29,9 +29,6 @@ import ./blockexchange
 logScope:
   topics = "dagger node"
 
-const
-  FileChunkSize* = 4096 # file chunk read size
-
 type
   DaggerError = object of CatchableError