he MK4i module moves the motors to a lower position where they are out of the way and better protected. Overall height and center of gravity are lower. The MK4i module also moves the wheel further into the corner of the chassis for a wider wheelbase which results in a more stable robot. Because the wheel is moved into an area the frame would typically occupy, the MK4i includes a secondary plate to properly box in the chassis.

Other Highlights of the MK4i module include:
On-axis steering encoder (zero backlash, module can be disassembled/reassembled without resetting encoder offset)
All plates made out of 7075-T6 aluminum
All steel gears
All moving parts are protected under top plate
Includes secondary plate to box in frame
10-32 mounting holes on main plate for subsystems (e.g., collector)
15mm width steering belt
Encoder guard to protect the steering encoder
Same frame-to-floor height as previous Swerve Drive Specialties modules
Same L1 - L3 drive ratios as the MK4 module
No 3D printed parts
Cable-tie “nubs” keeps cable-ties in place
Bottom and top mounted chassis options
Includes wheel tread cut-to-length, drilled, and pre-installed on wheel
Includes all hardware, including hardware to mount module to robot
 
The MK4i module has many parts in common with the MK4 module. Kits to convert the MK4 to MK4i are available.
The MK4i module ships unassembled and does not include the motors or encoder. The 1.5" width billet wheel is included.
REV Robotics NEO motors or Vex Robotics Falcon 500 motors are recommended for the MK4i module. CIM motors are not compatible with the MK4i due to their larger diameter. The MK4i module is available with either NEO 8mm bore pinions, or Falcon 500 spline bore pinions.
The steering gear ratio of the MK4i is 150/7:1. The MK4i is available in 3 different drive gear ratios. The table below shows the drive gear ratios and free speeds with NEO and Falcon 500 motors. L1 and L2 ratios are the most popular ratios and are suitable for standard full weight competition robots. The L3 ratio is more aggressive and is recommended for light weight robots.


The module easily mounts to common 2X1 frame material. The module main plate typically mounts on top of the robot chassis, however, there is also clearance to mount the chassis on top of the module main plate to maximize ground clearance. 
Weights:
MK4i module with NEO motors - 6.0 pounds (Includes encoder, lower mounting plate, mounting hardware, wires, etc)
MK4i module with Falcon 500 motors - 6.3 pounds (Includes encoder, lower mounting plate, mounting hardware, wires, etc)