diff --git a/sfc/slicer.py b/sfc/slicer.py
index 871f089..7906e0f 100755
--- a/sfc/slicer.py
+++ b/sfc/slicer.py
@@ -92,8 +92,9 @@ def dump_level(wires, z):
 
 def usage():
 	print >>sys.stderr, "usage:", sys.argv[0], \
-	    "[-a (top|bottom)(+|-)offset] [-f] [-h height]" + \
-	    "\t[-b piece_distance] [-o z_offset] [-s max_step] file.stl"
+	    "[-a (top|bottom)(+|-)offset] [-f] [-h height]\n" + \
+	    "\t[-m tolerance] [-p piece_distance] [-o z_offset] "+ \
+	    "[-s max_step] file.stl"
 	sys.exit(1)
 
 
@@ -106,7 +107,7 @@ stdout = os.dup(1)
 os.dup2(2, 1)
 sys.stdout = os.fdopen(stdout, "w")
 
-opts, args = getopt.getopt(sys.argv[1:], "a:e:fh:o:p:s:")
+opts, args = getopt.getopt(sys.argv[1:], "a:e:fh:m:o:p:s:")
 for opt, arg in opts:
 	if opt == "-a":
 		if arg[0:3] == "top":
@@ -115,6 +116,8 @@ for opt, arg in opts:
 			align_bottom = float(arg[6:])
 		else:
 			usage()
+	elif opt == "-m":
+		mech_eps = float(arg)
 	elif opt == "-o":
 		end = float(arg)
 	elif opt == "-f":