Update index.rst
diff --git a/docs/source/index.rst b/docs/source/index.rst
index e756a3f..90a41d9 100644
--- a/docs/source/index.rst
+++ b/docs/source/index.rst
@@ -171,6 +171,9 @@
# set PDK_ROOT to the path you wish to use for the pdk
export PDK_ROOT=<pdk-installation-path>
+
+ # set the PDK variant depending on your shuttle, if you don't know leave it as default
+ export PDK=sky130B
# use volare to download the pdk
# To change the default pdk version you can export OPEN_PDKS_COMMIT=<pdk_commit>