I want to say this is a long-belly line but it isn’t; this has a long head with a fairly short belly. That probably sounds like I’m being pedantic, but hopefully it suggests the terms we use when talking about fly lines are not always handy.
The head dimensions for the GT125 are: 10ft front taper and tip; 22ft belly; 41ft rear taper. That gives a total head length of 74ft – certainly a long head in a line which is 125ft long. This is certainly a long fly line.
This is a 6-weight line, the dimensions used to classify a #6 line are extremely simple, almost primitive really, the front 30ft should weigh close to 16 grains or 10.4 grams. Beyond 30ft fly line makers can, according to the standard, do whatever they like – of course they don’t do whatever, but the line standard is not why they don’t.
Casting, this line starts like a conventional #6, with a familiar rod in my hand it feels like a ‘normal’ #6 line, I get to 32ft outside the tip ring, actually a good bit longer than 32ft, and this could be a 6-weight DT or conventional WF floating line. Then, assuming I can false-cast a long line that extravagant rear taper does all it can to help me, so the mass of line builds up slowly, the taper smoothing waves and wiggles from my rod helping me carry a long, long line, more than I can handle with my more conventional WF lines. To my mind the length of this line and the rear taper means it is designed for casting a full WF floating line as far as possible – at times!
The front end of the GT125 serves the needs of fishing pretty well, loops turn over smoothly and cleanly. At short and medium range I’d say the turnover seemed sweet and accurate rather than punchy, most likely down to the diameter of the tip. For ‘normal’ leaders, e.g. monofilament, that makes for a fine fishing line, for sink tips I’d want to cut the front taper a little. For fishers who work on their casting, who can carrying a long line and like to carry a long line and throw a floating WF line as far as possible this is pretty close to ideal.