About 4 years ago I needed a Syn bag because of the…
Temperature Rating: +35 to -40
Weight: +35 is about 3lbs and the 0 degree is about 5lbs
Price Paid: $260
About 4 years ago I needed a Syn bag because of the wet factor, down is wonderful but doesn't do well in a wet environment. So I was reading about different manufacturers and was impressed with how impressed Wiggy is with their products. So, I talked to people who used the Wiggy brand and found them impressed as well.
So I bought The FTSS -40 and it has been very good to me. It is kind of heavy compared to my down equipment, but for hunting and fishing camps (car camping) it is great. Two bags, one a 35 degree and the other a 0 degree, that zip together, or apart, makes it easy to control the sleeping temperature and they are easy to clean.
If you are looking for a multi season bag, this could be the best you can do, mid summer to mid winter. If it's good enough for Navy Seals, it's good enough for me.