diff --git a/examples/heat_exchanger.py b/examples/heat_exchanger.py
index 0e98b4d..910d550 100644
--- a/examples/heat_exchanger.py
+++ b/examples/heat_exchanger.py
@@ -48,7 +48,7 @@ with BuildPart() as heat_exchanger:
     tube_locations = [
         l
         for l in HexLocations(
-            apothem=(tube_diameter + tube_spacing) / 2,
+            radius=(tube_diameter + tube_spacing) / 2,
             x_count=exchanger_diameter // tube_diameter,
             y_count=exchanger_diameter // tube_diameter,
         )