diff --git a/docs/BOM.md b/docs/BOM.md
index 225dcb4..44b565c 100644
--- a/docs/BOM.md
+++ b/docs/BOM.md
@@ -166,7 +166,10 @@ Header facts (carrier board spec SP-11324-001 v1.3, Table 3-3 and 5-3; raw copy
   "TTL level", so if it is ever fed 5 V, first check that its idle TX reads ~3.3 V.
 - Power comes from the header's 3.3 V supply pin (1 or 17), a regulated rail on the carrier board. Not from a GPIO: a GPIO pin is a signal
   and is not meant to power anything.
-- **The second module (2026-10-14) speaks WitMotion's newer register protocol, not the 3-byte commands** in smart-serow's `IMU.md`:
+- **The second module (2026-10-14) is a different product: "WitMotion WT61 plus, TTL version"**, in different packaging. The WT61
+  datasheet v24-0429 (the KB's) describes the plain WT61 and may not apply to it; rates, defaults and commands below are what this module
+  did, not what that datasheet says. Its own manual is still to find.
+- **It speaks WitMotion's newer register protocol, not the 3-byte commands** in smart-serow's `IMU.md`:
   it ignored `FF AA 63`. It came at 9600 baud / 10 Hz (a rate the datasheet does not list). Commands are 5 bytes,
   `FF AA <register> <low> <high>`, each run as **unlock `FF AA 69 88 B5`, the write, save `FF AA 00 00 00`**, all at the module's
   current baud. Done on the car Orin, checking after each step: