diff --git a/src/m_mirror.scad b/src/m_mirror.scad
new file mode 100644
index 00000000..cc70e5d0
--- /dev/null
+++ b/src/m_mirror.scad
@@ -0,0 +1,16 @@
+function m_mirror(v) = 
+    let(
+        nv = v / norm(v),
+        txx = -2* nv[0] * nv[0],
+        txy = -2* nv[0] * nv[1],
+        txz = -2* nv[0] * nv[2],
+        tyy = -2* nv[1] * nv[1],
+        tyz = -2* nv[1] * nv[2],
+        tzz = -2* nv[2] * nv[2]
+    )
+    [
+        [1 + txx, txy, txz, 0],
+        [txy, 1 + tyy, tyz, 0],
+        [txz, tyz, 1 + tzz, 0],
+        [0, 0, 0, 1]
+    ];
\ No newline at end of file