STI Model

Check each part. < Ref. to INSPECTION , Rear Disc Brake Assembly. >
Clean the inside of the caliper body using brake fluid.
Fluid:

FMVSS No. 116, DOT3 or DOT4
Install the piston seal and the piston - disc brake.
1. Apply a coat of brake fluid to piston seal and install the piston seal to the groove inside caliper body.
2. Apply a coat of brake fluid to the piston sliding part of caliper body and the entire outer surface of the piston - disc brake.
  Fluid:
  
  FMVSS No. 116, DOT3 or DOT4
3. Apply a coat of grease to the piston boot and fit to the groove on the ends of piston - disc brake.
  Grease:
  
  An item contained in the pad kit or Nippon Grease NIGLUBE RX-2
4. Install the piston - disc brake to the caliper body.
  CAUTION: Do not force the piston - disc brake into the sliding part of caliper body.
  
  Fig 1: Installing Piston - Disc Brake To Caliper Body
  Courtesy of SUBARU OF AMERICA, INC.