The Companion Ring definitely lives up to its name as it is the great to use with a companion.  You will notice it has 2 rings. The smaller ring is to fit around the base of the penis and the larger ring is to fit around the testicles.  This will fit any sized man.  It has a vibrating bullet that attaches the 2 rings.  The vibrations will be felt by both partners.  There is also a pleasure nub that stimualtes the clitoris. 

It is powered by 4 watch size batteries which are included when you purchase this item. 

For more information about Penis Rings check out this article.