I acquired a vintage B & H Imperial Euphonium from an antique shop in New South Wales, Australia. The instrument came without the case or the mouthpiece so I was looking for a gig bag which could carry it. This gig bag from Protec is of a very high quality while fitting my budget well. As a soft gig bag, I think it is made to be very protective, as testified by the fact that my Euphonium hasn't been dented after it's been thrown around for more than a year now. I am also impressive by its generously sized side bag, which has plenty of room for oversize music scores, stationery and accessories. Some gig bags offer similar things but they are often too small to fit big music scores.
I also like the options between a single side strap and a pair of backpack straps. Though I have never used the latter, I think it is a very good feature for those who prefer carrying it this way, such as those who commute by bicycles.