diff --git a/compact/central_tracker.xml b/compact/central_tracker.xml
index a1aed4d51c5b367bdc6686e22d7dcf0c78c34c6e..3fe000904673180ca48d8384173231f68760e036 100644
--- a/compact/central_tracker.xml
+++ b/compact/central_tracker.xml
@@ -58,7 +58,6 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="TrackerEndcapInner_nLayers"          value="1"/>
     <constant name="TrackerEndcapOuter_nLayers"          value="3"/>
     <constant name="TrackerEndcapLayer_dz"               value="2*cm"/>
-    <constant name="TrackerEndcapModule_dz"              value="2.5*mm"/>
 
     <constant name="TrackerEndcapInner_zmin"            value="49*cm"/>
     <constant name="TrackerEndcapInner_zmax"            value="TrackerEndcapInner_zmin+TrackerEndcapLayer_dz"/>
@@ -117,21 +116,22 @@ total X0 0.24% per disk layer （4 sectors per disk):
     <constant name="TrackerEndcapOuterCone_length"     value="TrackerEndcapOuterCone_zmax - TrackerEndcapOuterCone_zmin"/>
 
 
-    <constant name="TrackerEndcap_NModules" value="12"/>
-    <comment> nmodules = np.pi/np.arcsin(frame_width*np.cos(tilt_angle)/2.0/R) </comment>
+    <comment> Barrel staves, nmodules = np.pi/np.arcsin(frame_width*np.cos(tilt_angle)/2.0/R) </comment>
     <constant name="TrackerBarrel_StaveTiltAngle" value="5.0*degree"/>
     <constant name="TrackerBarrelInner_NModules1" value="33"/>
     <constant name="TrackerBarrelInner_NModules2" value="36"/>
     <constant name="TrackerBarrelOuter_NModules1" value="62"/>
     <constant name="TrackerBarrelOuter_NModules2" value="68"/>
 
-
-    <constant name="TrackerEndcapInnerModOpeningAngle" value="360.0/TrackerEndcap_NModules*degree"/>
+    <comment> endcap panels, with z offset of 2.5mm each panel, and 0.5 degree overlap </comment>
+    <constant name="TrackerEndcap_NModules" value="12"/>
+    <constant name="TrackerEndcapModule_dz"               value="2.5*mm"/>
+    <constant name="TrackerEndcapInnerModOpeningAngle"    value="360.0/TrackerEndcap_NModules*degree + 0.5*degree"/>
     <constant name="TrackerEndcapInnerMod1_x1"            value="2.0*TrackerEndcapInner_rmin1*sin(TrackerEndcapInnerModOpeningAngle/2.0)"/>
     <constant name="TrackerEndcapInnerMod1_x2"            value="2.0*TrackerEndcapInner_rmax1*sin(TrackerEndcapInnerModOpeningAngle/2.0)"/>
     <constant name="TrackerEndcapInnerMod1_y"             value="TrackerEndcapInner_rmax1*cos(TrackerEndcapInnerModOpeningAngle/2.0) - TrackerEndcapInner_rmin1"/>
 
-    <constant name="TrackerEndcapOuterModOpeningAngle" value="360.0/TrackerEndcap_NModules*degree"/>
+    <constant name="TrackerEndcapOuterModOpeningAngle" value="360.0/TrackerEndcap_NModules*degree + 0.5*degree"/>
     <constant name="TrackerEndcapOuterMod1_x1"            value="2.0*TrackerEndcapOuter_rmin1*sin(TrackerEndcapOuterModOpeningAngle/2.0)"/>
     <constant name="TrackerEndcapOuterMod1_x2"            value="2.0*TrackerEndcapOuter_rmax1*sin(TrackerEndcapOuterModOpeningAngle/2.0)"/>
     <constant name="TrackerEndcapOuterMod1_y"             value="TrackerEndcapOuter_rmax1*cos(TrackerEndcapOuterModOpeningAngle/2.0) - TrackerEndcapOuter_rmin1"/>
diff --git a/compact/vertex_tracker.xml b/compact/vertex_tracker.xml
index 8028cc508537938d7ca1479804302a00f4aaabf8..5ae26567bcfcb76b0b50db4b4b708a9229d5b2d8 100644
--- a/compact/vertex_tracker.xml
+++ b/compact/vertex_tracker.xml
@@ -62,8 +62,9 @@ Simple carbon fiber support shell.
     <constant name="VertexEndcapLayer_dz"           value="2*cm"/>
     <constant name="VertexEndcapLayer_thickness"    value="min(3*cm,VertexEndcapLayer_dz-0.5*cm)"/>
 
-    <constant name="VertexEndcap_NModules" value="12"/>
-    <constant name="VertexEndcapModOpeningAngle"    value="360.0/VertexEndcap_NModules*degree"/>
+    <constant name="VertexEndcap_NModules"          value="12"/>
+    <constant name="VertexEndcapMod_dz"             value="2.5*mm"/>
+    <constant name="VertexEndcapModOpeningAngle"    value="360.0/VertexEndcap_NModules*degree + 0.5*degree"/>
     <constant name="VertexEndcapMod1_x1"            value="2.0*VertexTrackerEndcapP_rmin*sin(VertexEndcapModOpeningAngle/2.0)"/>
     <constant name="VertexEndcapMod1_x2"            value="2.0*VertexTrackerEndcapP_rmax*sin(VertexEndcapModOpeningAngle/2.0)"/>
     <constant name="VertexEndcapMod1_y"             value="VertexTrackerEndcapP_rmax*cos(VertexEndcapModOpeningAngle/2.0) - VertexTrackerEndcapP_rmin"/>
@@ -209,7 +210,7 @@ Simple carbon fiber support shell.
         <ring vis="TrackerVis"
           r="VertexTrackerEndcapP_rmin+VertexEndcapMod1_y/2.0"
           zstart="0.0"
-          nmodules="12" dz="2.5 * mm" module="Module1" />
+          nmodules="VertexEndcap_NModules" dz="VertexEndcapMod_dz" module="Module1" />
       </layer>
     </detector>
 
@@ -250,7 +251,7 @@ Simple carbon fiber support shell.
         <ring vis="TrackerVis"
           r="VertexTrackerEndcapN_rmin+VertexEndcapMod1_y/2.0"
           zstart="0.0"
-          nmodules="12" dz="2.5 * mm" module="Module1" />
+          nmodules="VertexEndcap_NModules" dz="VertexEndcapMod_dz" module="Module1" />
       </layer>
     </detector>