diff --git a/ffiwrapper/config.go b/ffiwrapper/config.go
index 1b01e9c1e..b0c3b02e8 100644
--- a/ffiwrapper/config.go
+++ b/ffiwrapper/config.go
@@ -1,7 +1,6 @@
 package ffiwrapper
 
 import (
-	"fmt"
 	"golang.org/x/xerrors"
 
 	"github.com/filecoin-project/specs-actors/actors/abi"
@@ -19,36 +18,20 @@ func sizeFromConfig(cfg Config) (abi.SectorSize, error) {
 	}
 
 
-	return SectorSizeForRegisteredProof(cfg.SealProofType)
+	return cfg.SealProofType.SectorSize()
 }
 
-// TODO: remove this method after implementing it along side the registered proofs and importing it from there.
-func SectorSizeForRegisteredProof(p abi.RegisteredProof) (abi.SectorSize, error) {
-	switch p {
-	case abi.RegisteredProof_StackedDRG32GiBSeal, abi.RegisteredProof_StackedDRG32GiBPoSt:
-		return 32 << 30, nil
-	case abi.RegisteredProof_StackedDRG2KiBSeal, abi.RegisteredProof_StackedDRG2KiBPoSt:
-		return 2 << 10, nil
-	case abi.RegisteredProof_StackedDRG8MiBSeal, abi.RegisteredProof_StackedDRG8MiBPoSt:
-		return 8 << 20, nil
-	case abi.RegisteredProof_StackedDRG512MiBSeal, abi.RegisteredProof_StackedDRG512MiBPoSt:
-		return 512 << 20, nil
-	default:
-		return 0, fmt.Errorf("unsupported registered proof %d", p)
-	}
-}
-
-func ProofTypeFromSectorSize(ssize abi.SectorSize) (abi.RegisteredProof, abi.RegisteredProof, error) {
+func SealProofTypeFromSectorSize(ssize abi.SectorSize) (abi.RegisteredProof, error) {
 	switch ssize {
 	case 2 << 10:
-		return abi.RegisteredProof_StackedDRG2KiBPoSt, abi.RegisteredProof_StackedDRG2KiBSeal, nil
+		return abi.RegisteredProof_StackedDRG2KiBSeal, nil
 	case 8 << 20:
-		return abi.RegisteredProof_StackedDRG8MiBPoSt, abi.RegisteredProof_StackedDRG8MiBSeal, nil
+		return abi.RegisteredProof_StackedDRG8MiBSeal, nil
 	case 512 << 20:
-		return abi.RegisteredProof_StackedDRG512MiBPoSt, abi.RegisteredProof_StackedDRG512MiBSeal, nil
+		return abi.RegisteredProof_StackedDRG512MiBSeal, nil
 	case 32 << 30:
-		return abi.RegisteredProof_StackedDRG32GiBPoSt, abi.RegisteredProof_StackedDRG32GiBSeal, nil
+		return abi.RegisteredProof_StackedDRG32GiBSeal, nil
 	default:
-		return 0, 0, xerrors.Errorf("unsupported sector size for miner: %v", ssize)
+		return 0, xerrors.Errorf("unsupported sector size for miner: %v", ssize)
 	}
 }
diff --git a/ffiwrapper/sealer_cgo.go b/ffiwrapper/sealer_cgo.go
index 63884163c..6764c3d96 100644
--- a/ffiwrapper/sealer_cgo.go
+++ b/ffiwrapper/sealer_cgo.go
@@ -313,7 +313,7 @@ func GenerateUnsealedCID(proofType abi.RegisteredProof, pieces []abi.PieceInfo)
 		sum += p.Size
 	}
 
-	ssize, err := SectorSizeForRegisteredProof(proofType)
+	ssize, err := proofType.SectorSize()
 	if err != nil {
 		return cid.Undef, err
 	}
diff --git a/mock/mock.go b/mock/mock.go
index bb5b07dec..d55b40f5a 100644
--- a/mock/mock.go
+++ b/mock/mock.go
@@ -35,7 +35,7 @@ type SectorMgr struct {
 type mockVerif struct{}
 
 func NewMockSectorMgr(threads int, ssize abi.SectorSize) *SectorMgr {
-	rt, _, err := ffiwrapper.ProofTypeFromSectorSize(ssize)
+	rt, err := ffiwrapper.SealProofTypeFromSectorSize(ssize)
 	if err != nil {
 		panic(err)
 	}