There are 2 different size hoops for the JANOME MB4. The Cap/ Hat Hoop Kit has a  Sewing Field of 270 mm x 203 mm (10.5" x 8"). Which is over 270% larger than the Janome Cap hoop.

The GIANT HOOP has a 270 mm x 336 mm sewing field (10.5" x 13.2"). Included with these kits are 2 mounting Brackets, instructions and a sample of SIA stabilizer. The Kit is complete and ready to embroider.

 

Once you buy a complete Kit with 2 mounting brackets, you can buy the other frame-only, at a great saving. These hoops are available to all Janome dealers, if they are interested.