Confused.sissy....

Please can someone help me, my Mistress has decided that I should get a smaller cage, I presently use a nice pink CB3000, to prevent any kind of arousal and to be better for me to wear. She would also like me to use one with the tube that runs inside my pens. There seems to be so many on the market, I don't want to spend a fortune and get it wrong....I would really appreciate a little advice on this matter.