Hi James Late 2016, will mean Caterham branded remade (not refurbished Ford) Sierra caliper. My experience with these calipers is mixed. The first pair I had where fine, they came as a warranty replacement for a 2015 kit which has been supplied with refurbished Ford items. I have seen photos of a friends car where he had a rear caliper fire within weeks of IVA / PBC, and my recent (this week) experience of leaks from brand new item for my current build. My leaking new caliper would normally be no problem, but apparently Caterham supply chain for them has run dry due to China lockdown, and I had a choice wait of a part with no ETA or looks for an alternative. I decided to rebuild my new kit calipers with parts from BiggRed. Obviously I started with the leaking caliper, which dismantled very easy, only to find swarf in the caliper a scratched piston and what was described by BiggRed as a "slack seal". The rebuild using BiggRed parts was successful, so I decided with what I found to rebuild the other side. This time (and the point of my post) removing the piston was a pig, it took a lot of persuasion to get out, much like your piston is taking to get in. I had the luxury of working on the bench and yet it still took a good half an hour, your working under the arch, with the brake line connected. All I can say is persevere, and keep the pressure on with the backplate of the wind back tool, so its the pressure from the tool that pushes the piston in as you wind back the adjuster nut (inside the caliper). And yes clockwise is correct to wind the piston into the caliper. Can you not assemble the tool in the caliper so it fits, if not then the grinder sounds like a plan (I hate tool abuse). Chris.