You really should measure your cylinder with a caliper. Most of the ones I have will interchange with each other but to buy one without trying it or measuring it is a gamble. Go to www.rugerforum.com
and put a WTB in the classified section and you should have a response in a day or so. Depending on weather you have an old model or a new model single six it will runn you from $40 to $125. Good luck!