diff --git a/spaceKLIP/imagetools.py b/spaceKLIP/imagetools.py
index 0c6a9bdf..77f62b8a 100644
--- a/spaceKLIP/imagetools.py
+++ b/spaceKLIP/imagetools.py
@@ -2012,7 +2012,7 @@ def align_frames(self,
         mask_override : str, optional
             Mask some pixels when cross correlating for shifts
         msk_shp : int, optional
-            Shape (height or radius) for custom mask invoked by "mask_override"
+            Shape (height or radius, or [inner radius, outer radius]) for custom mask invoked by "mask_override"
         shft_exp : float, optional
             Take image to the given power before cross correlating for shifts, default is 1. For instance, 1/2 helps align nircam bar/narrow data (or other data with weird speckles)
         kwargs : dict, optional
@@ -2034,6 +2034,18 @@ def align_frames(self,
             os.makedirs(output_dir)
 
         # useful masks for computing shifts:
+        def create_annulus_mask(h, w, center=None, radius=None):
+
+            if center is None: # use the middle of the image
+                center = (int(w/2), int(h/2))
+            if radius is None: # use the smallest distance between the center and image walls
+                radius = min(center[0], center[1], w-center[0], h-center[1])
+
+            Y, X = np.ogrid[:h, :w]
+            dist_from_center = np.sqrt((X - center[0])**2 + (Y-center[1])**2)
+
+            mask = (dist_from_center <= radius[0]) | (dist_from_center >= radius[1])
+            return mask
         def create_circular_mask(h, w, center=None, radius=None):
 
             if center is None: # use the middle of the image
@@ -2080,7 +2092,9 @@ def create_rec_mask(h, w, center=None, z=None):
                 maskfile = self.database.obs[key]['MASKFILE'][j]
                 mask = ut.read_msk(maskfile)
                 if mask_override is not None:
-                    if mask_override == 'circ':
+                    if mask_override == 'ann':
+                        mask_circ = create_annulus_mask(data[0].shape[0], data[0].shape[1], radius=msk_shp)
+                    elif mask_override == 'circ':
                         mask_circ = create_circular_mask(data[0].shape[0],data[0].shape[1], radius=msk_shp)
                     elif mask_override == 'rec':
                         mask_circ = create_rec_mask(data[0].shape[0],data[0].shape[1], z=msk_shp)
@@ -2093,7 +2107,7 @@ def create_rec_mask(h, w, center=None, z=None):
                     mask_temp = np.ones_like(data[0])
                 else:
                     mask_temp = mask
-                
+
                 # Align frames.
                 head, tail = os.path.split(fitsfile)
                 log.info('  --> Align frames: ' + tail)