Hope phenolic caliper pistonreplacement piston for hope disc brake calipers the new hope piston is a phenolic resin which drops a few grams off the brake this phenolic material also aids the heat dissipation of the brake correct orientation for fitting there are two letters embossed on the piston these should face towards the pads ie out of the caliper this is the same as the square edged recess facing out the angled recess facing in one piston onlybuy hope components from chain reaction