diff --git a/README.md b/README.md
index 9c77c7b..4d192ea 100644
--- a/README.md
+++ b/README.md
@@ -119,7 +119,9 @@ This Bear Frame Upgrade 2.1 is compatible with the Full Bear Frame Upgrade 2.0 _
 
 ## Bill of materials
 
-[Read the BOM here](doc/bom.md).
+If you are building your Bear from scratch then [Read the BOM here](doc/bom.md).
+
+If you are upgrading a 2.0 Bear to a 2.1 Bear via the hardware upgrade kit then [Read the 2.0 - 2.1 upgrade BOM here](doc/2-0-to-2-1-upgrade-kit-bom.md).
 
 
 
diff --git a/doc/2-0-to-2-1-upgrade-kit-bom.md b/doc/2-0-to-2-1-upgrade-kit-bom.md
new file mode 100644
index 0000000..1f1cbc8
--- /dev/null
+++ b/doc/2-0-to-2-1-upgrade-kit-bom.md
@@ -0,0 +1,57 @@
+# Bear Frame Upgrade 2.0 -> 2.1
+
+## Bill of Materials
+
+### Hardware
+
+| Part     | Quantity | Spare | Detail | Example Links |
+|----------|:--------:|:--------:|--------|---------------|
+| Tee-nuts M5 | 31 | 1 |30x for printed parts | Custom made |
+| M5x8mm button head screw (ISO 7380) | 5 | 1 | 4x for printed parts | [Openbuilds](http://openbuildspartstore.com/low-profile-screws-m5-10-pack/)<br>[McMaster-Carr](https://www.mcmaster.com/#91239a222/=1clymbr) |
+| M5x10mm button head screw (ISO 7380) | 17 | 1 | 16x for printed parts | [Openbuilds](http://openbuildspartstore.com/low-profile-screws-m5-10-pack/)<br>[McMaster-Carr](https://www.mcmaster.com/#97763a820/=1cltxg0) |
+| M5x12mm button head screw (ISO 7380) | 10 | 1 | 1x for Y motor mount,<br>8x for Y rod holders | [Openbuilds](http://openbuildspartstore.com/low-profile-screws-m5-10-pack/)<br>[McMaster-Carr](https://www.mcmaster.com/#91239a228/=1cm065c) |
+| M5x16mm button head screw (ISO 7380) | 2 | 1 | 1x for Y motor mount | [McMaster-Carr](https://www.mcmaster.com/92095a212) |
+| M3x10mm socket head screw (ISO 4762) | 12 | 0 | 1x for Y motor mount,<br>2x for Y belt holder,<br>8x for Z motor mounts,<br>1x for PSU lower mount | [McMaster-Carr](https://www.mcmaster.com/91239A115) |
+| M3x14mm socket head screw (ISO 4762) | 2 | 0 | 2x for RAMBo base mounts | [McMaster-Carr](https://www.mcmaster.com/91292a027) |
+| M3x18mm socket head screw (ISO 4762) | 4 | 1 | 3x for Y motor mount | [McMaster-Carr](https://www.mcmaster.com/91292a029) |
+| M3x25mm socket head screw (ISO 4762) | 7 | 0 | 1x for Y idler,<br>6x for Y bearing holders | [McMaster-Carr](https://www.mcmaster.com/91292a020) |
+| M3x30mm socket head screw (ISO 4762) | 1 | 0 | 1x for Y idler | [McMaster-Carr](https://www.mcmaster.com/91292a022) |
+| Set screw M4x5mm | 14 | 2 | 12x for end-caps | [McMaster-Carr](https://www.mcmaster.com/92015a111) |
+| Dowel pin 2.95x16mm | 2 | 1 | 1x for Y idler tensioner.<br>:pushpin: Cut an M3 screw if you can't find one ||
+| M3 hex nuts (ISO 4032) | 2 | 0 | 2x for Rambo base mounts | [McMaster-Carr](https://www.mcmaster.com/91828a211) |
+| M3 nylock nut (ISO 10511) | 3 | 1 | 2x for Y idler | [McMaster-Carr](https://www.mcmaster.com/93625a100) |
+| M3 square nut (DIN 562) | 2 | 0 | 1x for Y belt holder,<br>1x for lower PSU mount | [McMaster-Carr](https://www.mcmaster.com/97258A101) |
+| M3 flat washer (ISO 7089) | 2 | 1 | 1x for Y idler | [McMaster-Carr](https://www.mcmaster.com/93475A210/) |
+| Zip ties 2.5x100mm | 20 | 0 | 20x for cable management ||
+| Felt pad sticker | 4 | 0 | 4x for feet ||
+
+### Printed Parts
+
+| Part     | Quantity | Comment |
+|----------|:--------:|---------|
+| build_helper_y         | 1 | :warning: Print a single part                     |
+| build_helper_z         | 1 | :warning: Print a single part                     |
+| cable_clip_horizontal  | 2 |                                                   |
+| cable_clip_lcd         | 5 |                                                   |
+| cable_clip_vertical    | 6 |                                                   |
+| foot                   | 4 |                                                   |
+| lcd_support_a          | 1 |                                                   |
+| lcd_support_b          | 1 |                                                   |
+| psu_lower_mount        | 1 | File name may vary depending your PSU version     |
+| psu_upper_mount        | 2 | File name may vary depending your PSU version     |
+| rambo_base_lower_mount | 1 |                                                   |
+| rambo_base_upper_mount | 1 |                                                   |
+| rambo_hinge_lower      | 1 | File name may vary depending your printer version |
+| rambo_hinge_upper      | 1 | File name may vary depending your printer version |
+| y_bearing_holder       | 3 |                                                   |
+| y_belt_holder          | 1 |                                                   |
+| y_end_caps             | 2 | Total of 4 printed parts                          |
+| y_idler_mount          | 1 |                                                   |
+| y_idler_tensioner      | 1 |                                                   |
+| y_motor_endstop_mount  | 1 | :warning: Only for MK2(S) or MK2.5(S)             |
+| y_motor_mount          | 1 |                                                   |
+| y_rod_holder           | 4 |                                                   |
+| z_end_caps             | 1 | Total of 2 printed parts                          |
+| z_leadscrew_cap        | 2 |                                                   |
+| z_motor_mounts         | 1 | Total of 2 printed parts                          |
+| z_tops                 | 1 | Total of 2 printed parts                          |