MOST DOGS, BUT ESPECIALLY CAVALIERS, LOVE TO PICK STUFF UP, CARRY IT AROUND IN THEIR MOUTH, AND PERHAPS SWALLOW AN OBJECT THAT MAY BE POISONOUS, TOXIC OR DANGEROUS. WE HAVE FOUND THAT THE 'OUTFOXHOOD' WORKS REMARKABLY WELL, YOUR CAVALIER CAN BREATH, SEE OUT, AND YET CAN'T PICK UP A SINGLE THING. LOOK AT THE PICTURES ON THEIR WEBSITE, YOU'LL SEE WHAT WE MEAN. SIZES ARE ON THE SITE, BUT SIZE 'XSO' WORKS BEST FOR PUPPIES AND 'SO' WORKS BEST FOR THE ADULTS. THEIR WEBSITE IS WWW.OUTFOXFORDOGS.COM, THERE YOU WILL SEE PICTURES OF VARIOUS SIZE DOGS, AND THERE IS A RUBY CAVALIER IN THE 'LINEUP'. MEASURING TIPS ARE THERE AS WELL. A SMALL INVESTMENT TO HELP PREVENT YOUR CAVALIER OR YOUR OTHER DOGS AVOID A HARMFUL OR DANGEROUS OBJECT FROM BEING SWALLOWED.