diff --git a/smr/build-fresh.py b/smr/build-fresh.py
index 5819516..92b5128 100644
--- a/smr/build-fresh.py
+++ b/smr/build-fresh.py
@@ -20,10 +20,14 @@ parser.add_argument('-m', '--multipole', action='store_true',
                     help='Whether to use multipole cross sections')
 parser.add_argument('-t', '--tallies', choices=('cell', 'mat'), default='cell',
                     help='Whether to use distribmats or distribcells for tallies')
+parser.add_argument('-r', '--rings', type=int, default=10,
+                    help='Number of annular regions in fuel')
+parser.add_argument('-a', '--axial', type=int, default=196,
+                    help='Number of axial subdivisions in fuel')
 args = parser.parse_args()
 
 
-geometry = core_geometry()
+geometry = core_geometry(args.rings, args.axial)
 
 #### "Differentiate" the geometry if using distribmats
 if args.tallies == 'mat':
diff --git a/smr/smr/assemblies.py b/smr/smr/assemblies.py
index d673127..d53ce05 100644
--- a/smr/smr/assemblies.py
+++ b/smr/smr/assemblies.py
@@ -120,8 +120,8 @@ def make_assembly(name, universes):
     return universe
 
 
-def assembly_universes():
-    pins = pin_universes()
+def assembly_universes(num_rings=10, num_axial=196):
+    pins = pin_universes(num_rings, num_axial)
 
     # Create dictionary to store assembly universes
     univs = {}
diff --git a/smr/smr/core.py b/smr/smr/core.py
index 5352cf7..d6879a7 100644
--- a/smr/smr/core.py
+++ b/smr/smr/core.py
@@ -12,8 +12,8 @@ from .assemblies import assembly_universes
 
 #### CONSTRUCT MAIN CORE LATTICE
 
-def core_lattice():
-    assembly = assembly_universes()
+def core_geometry(num_rings=10, num_axial=196):
+    assembly = assembly_universes(num_rings, num_axial)
     reflector = reflector_universes()
 
     core = openmc.RectLattice(name='Main core')
@@ -100,12 +100,6 @@ def core_lattice():
     universes[8, 6] = reflector['8,6']
 
     core.universes = universes
-    return core
-
-
-def core_geometry():
-    # Create core lattice
-    core = core_lattice()
 
     root_univ = openmc.Universe(universe_id=0, name='root universe')
 
diff --git a/smr/smr/pins.py b/smr/smr/pins.py
index d3d19dd..cee7cbc 100644
--- a/smr/smr/pins.py
+++ b/smr/smr/pins.py
@@ -142,7 +142,7 @@ def make_pin_stack(name, zsurfaces, universes, boundary, pin_universe):
     return universe
 
 
-def pin_universes(num_rings=10):
+def pin_universes(num_rings=10, num_axial=196):
     # Create dictionary to store pin universes
     univs = {}
 
@@ -683,8 +683,7 @@ def pin_universes(num_rings=10):
 
     # Determine z position between each fuel pellet, omitting the surfaces
     # corresponding to the very bottom and top of the active fuel length
-    n_pellets = 196
-    axial_splits = np.linspace(bottom_fuel_rod, top_active_core, n_pellets + 1)[1:-1]
+    axial_splits = np.linspace(bottom_fuel_rod, top_active_core, num_axial + 1)[1:-1]
     axial_surfs = [openmc.ZPlane(z0=z) for z in axial_splits]
 
     # Get z-cylinder surfaces for each ring