diff --git a/docs/nixos_build_spec.md b/docs/nixos_build_spec.md
index 5a4a2ed..da6b320 100644
--- a/docs/nixos_build_spec.md
+++ b/docs/nixos_build_spec.md
@@ -34,7 +34,9 @@ WIPE + install NixOS here:
   - /dev/sda1: Microsoft reserved partition (~15MiB)
   - /dev/sda2: NTFS label "Back Up" (keep)
 - TempBackup (ext4) UUID=4f9c4bd5-fea5-408f-9370-731fc095da3f (~465GiB/500GB) (KEEP)
-  - NOTE: device name may appear as /dev/sdb or /dev/sdc depending on boot/USB order; identify by UUID/label.
+  - Model: WD5000BEVT-22ZAT
+  - Serial: WD-WXNY08ND2684
+  - NOTE: device name may appear as /dev/sdb or /dev/sdc depending on boot/USB order; identify by UUID/label/model.
 - Integral300 (ext4) UUID=27febd74-20aa-4a3a-92c1-6fdd1ad7e88e (~298GiB/320GB) (mount at /data)
   - NOTE: device name may change; config always uses /dev/disk/by-uuid.
 - /dev/sde (160GB) ext4 label "XPSystemDrive" (keep)