Silastic Ring in Gastric Bypass The successful utilization of silastic gastric rings to control the stoma size in vertical banded gastroplasty, has led bariatric surgeons to use both silastic rings and Marlex bands in gastric bypass procedures, (eg. Fobi Pouch) to maintain the stoma size and reduce stretching. Ring circumference is typically larger than that provided for in primary bariatric procedures, so that their regulatory effect is only triggered after some degree of stretching of the pouch has occurred. A Silastic Ring Gastric Bypass with a 6.0 cm ring achieves equivalent weight loss to one with a 5.5 cm ring, but with better quality of eating, and less prospect of requiring ring removal. However, there remains a small proportion of patients in whom a 6.0 cm ring is poorly tolerated. For this reason a 6.5 cm ring should be tested.