diff --git a/msr.go b/msr.go
index d1f1a55..3f949f3 100644
--- a/msr.go
+++ b/msr.go
@@ -27,7 +27,7 @@ func MSRPaths() ([]string, error) {
 }
 
 // MSRs attemps to return all available MSRs.
-func MSRs(onErr func(error)) []*MSR {
+func MSRs(flag int, perm os.FileMode, onErr func(error)) []*MSR {
 	paths, err := MSRPaths()
 	if err != nil {
 		onErr(err)
@@ -35,7 +35,7 @@ func MSRs(onErr func(error)) []*MSR {
 	}
 	msrs := []*MSR{}
 	for _, path := range paths {
-		msr, err := NewMSR(path)
+		msr, err := NewMSR(path, flag, perm)
 		if err != nil {
 			onErr(err)
 			continue
@@ -51,8 +51,8 @@ type MSR struct {
 }
 
 // NewMSR returns a MSR.
-func NewMSR(path string) (*MSR, error) {
-	f, err := os.OpenFile(path, os.O_RDWR, 0660)
+func NewMSR(path string, flag int, perm os.FileMode) (*MSR, error) {
+	f, err := os.OpenFile(path, flag, perm)
 	if err != nil {
 		return nil, err
 	}
diff --git a/msr_test.go b/msr_test.go
index 9e29dfe..c653e16 100644
--- a/msr_test.go
+++ b/msr_test.go
@@ -1,6 +1,7 @@
 package perf
 
 import (
+	"os"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -15,7 +16,7 @@ func TestMSR(t *testing.T) {
 	msrs, err := MSRPaths()
 	require.Nil(t, err)
 
-	msr, err := NewMSR(msrs[0])
+	msr, err := NewMSR(msrs[0], os.O_RDWR, 0660)
 	require.Nil(t, err)
 
 	// TODO: This may only work on certain architectures :(
@@ -28,7 +29,7 @@ func TestMSR(t *testing.T) {
 }
 
 func TestMSRs(t *testing.T) {
-	MSRs(func(err error) {
+	MSRs(os.O_RDWR, 0660, func(err error) {
 		require.Nil(t, err)
 	})
 }