An X-Carriage kit is required to install the Bondtech upgrade kit for Prusa i3 MK3S.
This SLS version is for users working with closed chambers to heat the air inside up to 100°C.
The FFF version, made of HT-PLA would deform under such conditions.
The kit contains:
SLS
X-Carriage front
SLS X-Carriage rear
5 x M3x10 screws
5x M3 square
nut 1x M3 nut