The Robot basket plug is handy for pre-heating the piston or for verifying that the pressure gauge is functioning.

The plug is made from food grade silicone (BPA free), same material as the Robot piston seals are made of.

Pre-heating the Robot piston

1. For the piston pre-heating, wipe the basket clean to make sure it is free of coffee particles.
2. Push the blank plug down to the bottom of the basket then add the hot water up to the top as usual.  
3. Insert into the machine and you can hold the levers down for 30-60 seconds to warm up the piston.  
4. Remove the portafilter, dump out the water and pull the plug out.

Now the piston is preheated, so you can continue with the standard process.