diff --git a/Mu2eG4/geom/bfgeom_no_field.txt b/Mu2eG4/geom/bfgeom_no_field.txt
new file mode 100644
index 0000000000..cf0ecf61da
--- /dev/null
+++ b/Mu2eG4/geom/bfgeom_no_field.txt
@@ -0,0 +1,53 @@
+//
+// Variant of the BField system with zero magnetic field everywhere.
+//
+// BField information maintained as a separate file.
+//
+// Warning:
+//  There are multiple points of maintenance when you change bfield.innerMaps
+//  There are multiple points of maintenance when you change bfield.innerMaps
+//    - bfgeom_v01.txt           ( the base geometry  )
+//    - bfgeom_no_ds_v01.txt     ( DS map removed     )
+//    - bfgeom_reco_v01.txt      ( only maps needed for reconstruction )
+//    - bfgeom_no_tsu_ps_v01.txt ( PS and TSu maps removed.
+//    - bfgeom_no_field.txt      ( Magnetic field is zero everywhere )
+//
+
+// Form of DS field: 0 is full field;
+//                   1 is full upstream, const downstream;
+//                   2 is const throughout
+int detSolFieldForm = 0;
+
+vector<string> bfield.innerMaps = {};
+
+// Value of the uniform magnetic field with the DS volume (only for
+// detSolFieldForm>0)
+double toyDS.bz            = 0.0;
+
+// Gradient of field in DS2 volume. Applied only in the case
+// of detSolFieldForm=1 or detSolFieldForm=2.
+double toyDS.gradient      = 0.0; // Tesla/m
+
+// This is recommended field map. See geom_mecofield.txt to use the meco field.
+string bfield.format  = "G4BL";
+
+// The other option is "meco"
+string bfield.interpolationStyle = trilinear;
+
+int  bfield.verbosityLevel =  0;
+bool bfield.writeG4BLBinaries     =  false;
+
+vector<string> bfield.outerMaps = {};
+
+// This scale factor is of limited use.
+// It can make approximate sense to scale the PS field to get a rough
+// answer; the answer will be wrong in detail.
+// It never makes sense to scale the TS field.
+// Not sure if it ever makes sense to scale the PS field.
+double bfield.scaleFactor = 0.0;
+
+//
+// This tells emacs to view this file in c++ mode.
+// Local Variables:
+// mode:c++
+// End:
diff --git a/Mu2eG4/geom/geom_common_extracted.txt b/Mu2eG4/geom/geom_common_extracted.txt
index b0abd91e92..32527a8542 100644
--- a/Mu2eG4/geom/geom_common_extracted.txt
+++ b/Mu2eG4/geom/geom_common_extracted.txt
@@ -1,8 +1,11 @@
-// Top level geometry file for extracted detector cosmics running
+// Top level geometry file for extracted detector cosmics running with no magnetic field
 
 // Start from recent baseline geometry
 #include "Offline/Mu2eG4/geom/geom_common_current.txt"
 
+// Set the magnetic field to zero everywhere.
+#include "Offline/Mu2eG4/geom/bfgeom_no_field.txt"
+
 // Special - for garage position!
 bool inGaragePosition   = true;
 double garage.zOffset   = 14000.0;  // for creating special garageFakeDS(2/3)Vacuum volume