A handler and her Golden Retriever tracking on a 30 foot long line.
BioThane long lines come up in just about every training conversation, and for good reason: they're waterproof, they rinse clean in seconds, and they shrug off mud that would ruin a nylon line. But once you start shopping, the questions pile up fast. Which width? How long?
Honestly, it depends on your dog and what the two of you are doing together. There's no single right answer, but there's probably a right answer for you, and it isn't hard to find. Let's walk through it.
Picking a Width
Width changes two things: how much the line can handle, and how it feels in your hand when your dog hits the end of it at full speed. Here's the rundown.
Judith's Akita, Apple, working a trial nose work search on a 15 foot long line.
The Widths We Offer
1/4-inch round (rope): The narrowest rope option, best suited to small to medium dogs (roughly 15-30 pounds) when you prefer a rope-style line. One thing to know up front: round lines are fastened with solid brass clamps, which makes them a bit heavier than flat lines. Worth considering if your dog is on the sensitive side.
5/16-inch round (rope): A touch more strength than the 1/4-inch, still comfortable to handle. Same story on weight: solid brass clamps mean it weighs a bit more than a comparable flat line.
3/8-inch flat: A favorite everyday width for small dogs and plenty of medium ones. It coils easily, clips on and off without fuss, and never feels bulky. If you're not sure where to start, this is a good one.
1/2-inch flat: Probably our most versatile width, and the one we point most medium-to-large dog owners toward (think 40-65 pounds). The 1/2-inch line feels good in the hand and spreads pressure evenly when your dog pulls. Bonus: it's lighter than our 5/16-inch round lines, since flat gear has no clamps.
5/8-inch flat: Built for big, powerful dogs (65+ pounds). The 5/8-inch line gives you a solid, comfortable grip even when a strong puller hits the end of it. Hounds, Labs, and other large breeds do well here.
Matching Width to Your Dog
Weight is a decent starting point, but pulling power and enthusiasm matter just as much. A driven 40-pound Border Collie may genuinely need a 1/2-inch line, while a mellow 45-pound senior might be perfectly happy on 3/8-inch.
A rough guide to get you thinking:
- Under 12 pounds: 3/8-inch flat. The 1/4-inch round is generally too heavy for toy breeds.
- 12-40 pounds: 3/8-inch (flat). For dogs weighing 15-30 pounds, 1/4-inch (round/rope) is another option.
- 40-65 pounds: 5/16-inch (round/rope) or 1/2-inch (flat)
- 65+ pounds: 5/8-inch (flat) or, if well-trained, 5/16-inch (round/rope)
If you're torn between two widths, going slightly wider is usually the safer call. A line that's a touch too wide is comfortable; a line that's too thin when your dog locks eyes with a squirrel is not.
Piper on a 20 foot line during a walk, with the slack kept ready in hand.
Now, How Long?
Length really comes down to what you're training and where. There's no universal best, just what fits the work you and your dog actually do.
Length Options and Their Uses
4-10 feet: Great for controlled walking practice in town, or anywhere crowds and traffic make you want your dog close. Enough freedom to sniff a little ahead of you, easy to keep organized.
6-12 feet: The range most handlers reach for in nose work and scent work when the search is in a smaller space or indoors. Your dog has room to work the area, and the line stays manageable in tight quarters.
10-15 feet: For nose work and scent work in large, open areas, most people prefer 10 to 15 feet. Plenty of room to search, without a mile of line to gather in.
12-20 feet: The sweet spot for a lot of handlers. Your dog gets real room to explore on hikes and park trips, and you're not spending the whole session untangling line. This range is excellent for building a reliable recall and letting your dog practice good choices at a distance.
20-40 feet: The range for AKC tracking, where the guideline is at least 20 feet and no more than 40. It's also where serious distance work and advanced recall training live, and the longest lines suit Schutzhund (IGP, IPO) tracking, herding, or big open fields where a dog needs room to decompress. We also offer custom lengths if you need something outside the standard lineup.
Matching Length to Your Training Goals
Here's how length maps to the most common goals.
Jo's Weimaraner on a 40 foot line during tracking practice in South Africa.
For Recall Training
Start with a 15-20 foot line. It's long enough that distractions actually matter, but short enough that you can walk over and collect your dog for the walk of shame when they decide not to come (it happens to everyone). Your dog learns to check in even when something interesting is going on, and the line is your safety net the whole time.
For Hiking and Exploration
A 15-20 foot line is usually right for trails. Your dog can investigate smells and terrain while staying close enough for you to handle rocky sections, step aside for other hikers, and keep everyone safe. Much past 20 feet gets clumsy in the trees.
For Nose Work, Scent Work, and Tracking
There's no single length here, because the right one depends on the search. For nose work and scent work, most handlers use 6-12 feet in smaller or indoor areas, and 10-15 feet when they're working large, open ground. For AKC tracking, plan on at least 20 feet and no more than 40. At those distances the line is mostly a backup while your dog works independently.
For Everyday Freedom
If you just want to give your dog more say in your daily walks, a 12-15 foot line hits a happy middle: freeing for them, manageable for you.
Why BioThane Works So Well for This
A quick word on the material itself, because it's a big part of why handlers keep coming back to it.
BioThane is waterproof and non-porous, so water, mud, and odors sit on the surface instead of soaking in. After a soggy field session, a rinse is all it takes. No soaking, no scrubbing, no lingering swamp smell in your car.
It also shrugs off the landscape: BioThane doesn't attract cactus thorns, grass burrs, or pine needles, so you're not stopping every ten minutes to pick debris off your line. Anyone who has untangled a nylon line after a desert session knows exactly how much that matters.
And unlike leather, there's no conditioning, no careful drying, no special treatment. It just keeps working, season after season.
Cortnie's dog, Caoimhe, testing a 15 foot line on a foggy Maine beach.
Making the Call
Our honest advice: pick for your most common use first. If you train in open fields most weekends but walk the neighborhood on weekdays, buy for the field and keep a short leash for town. Trying to make one line do everything usually means it does nothing well.
Same with width. If your dog sits between two sizes, weigh their pulling style more than the number on the scale. A stocky, powerful 45-pound dog may genuinely need a 1/2-inch, while a lean 50-pounder with good manners might be fine on 3/8-inch.
Still Not Sure?
Totally fair, especially if this is your first long line. You're welcome to reach out to us and tell us about your dog and what you're working on. We help with this every day, and we're happy to give you a real answer rather than a spec sheet.
One reassuring thing: there's rarely one perfect choice, but there's usually a range of good ones. A line that's slightly longer or a touch wider than ideal will still serve you well (and it's often kinder on the hands, too). You don't need perfection, just a good match.
The fact that you're thinking it through at all puts you ahead. A line chosen with a little care tends to last for years and make every session easier. Whatever you're working on, recall, trail freedom, or field skills, the right long line quietly does its job in the background while you and your dog get on with the fun part.