Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download FPS Mesh Tool Free.
FPS Mesh Tool v1.2.5
FPS Mesh Tool v1.2.4
FPS Mesh Tool makes it quick and easy to prepare any skinned mesh for use in an FPS. It splits your base mesh into separate submeshes for the body, head, and arms, allowing you to apply different materials (eg invisible) to the arms, head, or body as needed. This works beautifully for transitions between first and third person, and is fully compatible with the full body awareness features of Opsive’s Ultimate Character Controller and UFPS. Additionally, FPS Mesh Tool can create meshes that only include the body parts you choose, which makes creation of FPS arms a snap from any skinned mesh.
* Works with Opsive’s Ultimate Character Controller.
* Runtime helpers make material toggling easier than ever.
* Quick and easy creation of FPS-ready mesh from any skinned mesh.
* Create FPS arms from any skinned mesh.
* Use standard humanoid animations with FPS arms.
* Optionally separate left and right arms and legs.
* Adjust bone weight and vertex count thresholds to fine tune body/arms/head borders.
* Preview results in realtime.
* Invisible shadow casting materials included.
* Support for blend shapes (requires Unity 5.3+)
* Works with all Unity versions from 5.3 to 2018.3.
FPS Mesh Tool works great with Unity character models from most sources. Here’s a list of some sources we’ve tried. In addition to the specific sources listed below, I’ve tested it with several standalone third-party characters on the asset store, and it’s worked great on all of them.
* Morph 3D (MCS) (Requires Unity 5.3+)
* New: IClone
* Runtime mesh generation features of UMA are not compatible with FPS Mesh Tool.
Support (Unity forum thread)