This is the:

Nexx Racing Mini-Z MR03 Front Suspension Spacer (RED) NX-197

NEXX Racing Mini-Z MR03 Front Suspension Spacer (RED) is used to replace MR03 plastic spacer when installing optional double A-arm V-LINE from NEXX RACING or PN Racing Double A-Arm Front Suspension or PN Racing MR3051 tower bars.  It eliminates the need of cutting off partial of the MR03 plastic spacer when using the optional front suspensions.

*** Do not work with stock Kyosho Mini-Z front suspension