Different size metal rings kit that are made to last a lifetime.
Use the rings individually or in combination, around the penis alone or the penis and scrotum.
It's especially important to not use a ring that's too tight.
Smallest: 4.5 cm in diameter, 3.3 cm inner diameter.
Medium: 5 cm in diameter, 3.9 cm inner diameter.
Large: 6.3cm diameter, 5.1cm inner diameter.