The OD of the core / center column is 24.5mm on mine. The reel is a snug fit onto this.
The tank itself has some ribs to hold in sheets if it's used that way (small clips slide onto those); the diameter inside those ribs is approx. 131.5mm with the ribs protruding ca. 1mm into the tank. I have a 2509N reel here which measures 128.5mm OD (outer rim). Its height is 105mm.
Note that the center column is raised off the bottom of the tank by about 22mm, so the inside of the reel is shorter overall than along the outer rim.