Thanks sir corrected. That's goes to prove how much I am in love with 1/2 A size. 

Thanks Col. You have a beautiful engine. I will be using my OS 61. Is this a stock muffler or bought separately. Looking for this type of muffler for my TT 30 heli engine as I would like to shift my raptor to a  Bel222 fibreglass fuse I had purchased some 6-7 years back.

Sir the Engine is slightly used but in excellent condition and compression came with this muffler recently from the original owner Parambir as a gift. I think he bought the muffler from towers.