diff --git a/Detector/DetCEPCv4/compact/Beampipe_o1_v01_01.xml b/Detector/DetCEPCv4/compact/Beampipe_o1_v01_01.xml
index ad3dc116fdba1d1a849f205a642ced6e9f3b48de..4b6d0ef0a0b00d7d66b9ecd0ade581b486def75d 100644
--- a/Detector/DetCEPCv4/compact/Beampipe_o1_v01_01.xml
+++ b/Detector/DetCEPCv4/compact/Beampipe_o1_v01_01.xml
@@ -15,16 +15,16 @@
   
   <!-- central tube -->
   <section type ="Center"                
-	   start="0*mm"                                  end="500*mm"
+	   start="0*mm"                                  end="TUBE_innerCylinder_zEnd_real"
            rMin1="TUBE_innerCylinder_rInner"  rMin2="TUBE_innerCylinder_rInner"       
 	   rMax1="TUBE_innerCylinder_rInner+TUBE_innerCylinder_thickness"        rMax2="TUBE_innerCylinder_rInner+TUBE_innerCylinder_thickness"
 	   material="G4_Be" name="IPInnerTube" />
 
   <!-- first cone -->
   <section type ="Center"
-           start="500*mm"                               end="700*mm"
-           rMin1="TUBE_innerCylinder_rInner"                          rMin2="17*mm"
-           rMax1="TUBE_innerCylinder_rInner+TUBE_innerCylinder_thickness" rMax2="17.5*mm"
+           start="TUBE_innerCylinder_zEnd_real"                               end="TUBE_firstCone_zEnd_real"
+           rMin1="TUBE_innerCylinder_rInner"                          rMin2="TUBE_firstCone_rInnerEnd_real"
+           rMax1="TUBE_innerCylinder_rInner+TUBE_innerCylinder_thickness" rMax2="TUBE_firstCone_rInnerEnd_real+TUBE_firstCone_thickness"
            material="G4_Be" name="IPInnerBulge" />
 
   <!-- second cylinder -->
diff --git a/Detector/DetCEPCv4/compact/tube_defs.xml b/Detector/DetCEPCv4/compact/tube_defs.xml
index 450b569cdc2f5d95fb2c2883241211c5b5cec315..a7ae55b70326cfcd2beb983f43143bb7da2f0665 100644
--- a/Detector/DetCEPCv4/compact/tube_defs.xml
+++ b/Detector/DetCEPCv4/compact/tube_defs.xml
@@ -1,14 +1,17 @@
 <define>
 
+  <constant name="TUBE_innerCylinder_zEnd_real" value="500*mm"/>
   <constant name="TUBE_innerCylinder_zEnd"      value="TUBE_IPInnerTube_end_z"/>
   <constant name="TUBE_innerCylinder_rInner"    value="TUBE_central_inner_radius"/>
   <constant name="TUBE_innerCylinder_thickness" value="TUBE_central_thickness"/>
 
+  <constant name="TUBE_firstCone_zEnd_real" value="700*mm"/>
   <constant name="TUBE_firstCone_zStart" value="TUBE_innerCylinder_zEnd"/>
   <constant name="TUBE_firstCone_zEnd" value="TUBE_IPInnerBulge_end_z"/>
   <constant name="TUBE_firstCone_rInnerStart" value="TUBE_innerCylinder_rInner"/>
   <constant name="TUBE_firstCone_rInnerEnd" value="TUBE_IPInnerBulge_end_innerradius"/>
   <constant name="TUBE_firstCone_thickness" value="0.5*mm"/>
+  <constant name="TUBE_firstCone_rInnerEnd_real" value="17*mm"/>
   <!--
      D. Jeans, update april 2017
      in this driver, we have to define the what I call the radial thickness