This same device is also known as a cock ring.

These objects range in shape and level of complication from a simple metal ring to a leather band with adjustable snap closures to just about anything you could imagine. Some have restraints for the balls as well, some have several adjustable bands, allowing circulation in the shaft of the penis to be cut off at multiple different points.

One disadvantage of the dick/cock ring is that men sometimes lose sensation as their circulation is cut off (what a surprise). They are not an apparatus whose use is really appropriate merely for pragmatic reasons (i.e., to extend the staying power of an erection). Rather, cock rings are most effective for men and couples who find arousal in sexual play concerned with bondage, domination, and other subjects external to the act itself.

Additionally, a simple snapping leather cock ring makes a good looking bracelet.