diff --git a/simpegEM/Analytics/FDEMcasing.py b/simpegEM/Analytics/FDEMcasing.py
index 8129f735..b6c7acf1 100644
--- a/simpegEM/Analytics/FDEMcasing.py
+++ b/simpegEM/Analytics/FDEMcasing.py
@@ -5,7 +5,8 @@ from simpegEM.Utils.EMUtils import k
 def getKc(freq,sigma,a,b,mu=mu_0,eps=epsilon_0):
     a = float(a)
     b = float(b)
-    return 2./np.pi * np.sqrt(b / a) * np.exp(-1j*k(freq,sigma,mu,eps)*(b-a))
+    # return 1./(2*np.pi) * np.sqrt(b / a) * np.exp(-1j*k(freq,sigma,mu,eps)*(b-a))
+    return np.sqrt(b / a) * np.exp(-1j*k(freq,sigma,mu,eps)*(b-a))
 
 def _r2(xyz):
     return np.sum(xyz**2,1)
diff --git a/simpegEM/Tests/test_FDEMCasing.py b/simpegEM/Tests/test_FDEMCasing.py
index 3efdcf52..12eedb14 100644
--- a/simpegEM/Tests/test_FDEMCasing.py
+++ b/simpegEM/Tests/test_FDEMCasing.py
@@ -1,6 +1,7 @@
 from SimPEG import Tests, Utils, np
 import simpegEM.Analytics.FDEMcasing as Casing
 import unittest
+from scipy.constants import mu_0
 
 
 n = 50.
@@ -8,41 +9,42 @@ freq = 1.
 a = 5e-2
 b = a + 1e-2
 sigma = np.r_[10., 5.5e6, 1e-1]
+mu = mu_0*np.r_[1.,100.,1.]
 srcloc = np.r_[0., 0., 0.]
 xobs = np.random.rand(n)+10.
 yobs = np.zeros(n)
-zobs = np.random.randn(n)
+zobs = np.random.randn(n) 
 plotit = False
 
 def CasingMagDipoleDeriv_r(x):
     obsloc = np.vstack([x, yobs, zobs]).T 
     
-    f = Casing._getCasingHertzMagDipole(srcloc,obsloc,freq,sigma,a,b)
-    g = Utils.sdiag(Casing._getCasingHertzMagDipoleDeriv_r(srcloc,obsloc,freq,sigma,a,b))
+    f = Casing._getCasingHertzMagDipole(srcloc,obsloc,freq,sigma,a,b,mu)
+    g = Utils.sdiag(Casing._getCasingHertzMagDipoleDeriv_r(srcloc,obsloc,freq,sigma,a,b,mu))
 
     return  f,g 
 
 def CasingMagDipoleDeriv_z(z):
     obsloc = np.vstack([xobs, yobs, z]).T 
     
-    f = Casing._getCasingHertzMagDipole(srcloc,obsloc,freq,sigma,a,b)
-    g = Utils.sdiag(Casing._getCasingHertzMagDipoleDeriv_z(srcloc,obsloc,freq,sigma,a,b))
+    f = Casing._getCasingHertzMagDipole(srcloc,obsloc,freq,sigma,a,b,mu)
+    g = Utils.sdiag(Casing._getCasingHertzMagDipoleDeriv_z(srcloc,obsloc,freq,sigma,a,b,mu))
 
     return  f,g 
 
 def CasingMagDipole2Deriv_z_r(x):
     obsloc = np.vstack([x, yobs, zobs]).T
     
-    f = Casing._getCasingHertzMagDipoleDeriv_z(srcloc,obsloc,freq,sigma,a,b)
-    g = Utils.sdiag(Casing._getCasingHertzMagDipole2Deriv_z_r(srcloc,obsloc,freq,sigma,a,b))
+    f = Casing._getCasingHertzMagDipoleDeriv_z(srcloc,obsloc,freq,sigma,a,b,mu)
+    g = Utils.sdiag(Casing._getCasingHertzMagDipole2Deriv_z_r(srcloc,obsloc,freq,sigma,a,b,mu))
     
     return f,g
 
 def CasingMagDipole2Deriv_z_z(z):
     obsloc = np.vstack([xobs, yobs, z]).T 
     
-    f = Casing._getCasingHertzMagDipoleDeriv_z(srcloc,obsloc,freq,sigma,a,b)
-    g = Utils.sdiag(Casing._getCasingHertzMagDipole2Deriv_z_z(srcloc,obsloc,freq,sigma,a,b))
+    f = Casing._getCasingHertzMagDipoleDeriv_z(srcloc,obsloc,freq,sigma,a,b,mu)
+    g = Utils.sdiag(Casing._getCasingHertzMagDipole2Deriv_z_z(srcloc,obsloc,freq,sigma,a,b,mu))
     
     return f,g