This is a LEGO Brick 1X1 . The "F" means that the brick is flat, so you can not connect any other brick over this one. The "R" means that the brick is round, unlike most of the other bricks I have uploaded. The size is the same as the small one I published in the past. ( 3 small bricks = 1 large brick) . The brick is similar with the brick 4646844 , but it does not need to be white.