Waterfly Running Belt Bum Bag waist pack for marathon, jogging and gym workouts

The essentials

A running belt bum bag is one of those small upgrades that can make a big difference once you stop carrying things in your pockets. The Waterfly Running Belt Bum Bag is designed to keep essentials close during jogging, running, training or even gym sessions, with a lightweight feel and a waistband that’s built to stay put.

On paper, it’s the kind of accessory that suits people who want their phone accessible without it bouncing around, and who prefer a slim waistband over bulkier storage. It’s also pitched as a night-friendly option thanks to a reflective logo, and it includes an independent headphone jack so your music can stay in step with your run.

Key points

At just 100g, the belt aims to avoid that “I’m wearing a weight” feeling. The waistband uses high elasticity and is paired with a buckle intended to prevent slipping and sagging, which matters if you do anything from steady jogs to longer sessions where your kit can start to shift.

Storage is split into three compartments. The main compartment is described as able to take mobile phones of all sizes, and the compartment layout is meant to let you organise a few extras at once—think your phone alongside headphones, keys, and even energy gels.

Where it shines day to day

The fabric is a lycra laminate described as soft, supple, absorbent, breathable and lightweight. It’s also hand-washable, with claims that it won’t pill, harden or warp—useful if you train regularly and your waist pack gets sweaty. There’s no promise of “it will never move”, but the combination of stretchy waistband and a secure buckle is clearly aimed at stability.

If you’re wondering about the practical feel: imagine starting a morning jog, slipping your phone into the main compartment and keys into a side space, then plugging in your headphones via the included headphone jack. The idea is that you can run with music and still reach your phone without having to stop and fish around.

Tech specs

• Weight: 100g
• Main compartments: 3
• Fabric: Lycra laminate

What to watch before you buy

There’s enough here to be a solid runner’s belt, but a couple of points are worth considering. First, the claim that the main compartment fits “cell phones of all sizes” is broad—so if you use a very large phone or thick case, it’s sensible to double-check your device dimensions against the pocket’s layout where possible.

Second, while the waistband is designed to resist slipping and sagging, comfort still depends on how it sits on your body during movement. If you’ve previously struggled with belts riding up, you may want to pay close attention to the fit when you first try it.

Who it’s for (and who should skip it)

It makes sense if you want a slim waist pack that can carry a phone plus small essentials during jogging, running, training, hiking, cycling, or gym workouts. It’s also a good fit if you train at night or in low light and care about visibility, since the reflective logo is specifically mentioned for safety.

You may want to skip it if you need a more structured pack for larger items beyond a phone, keys and gels, or if your training routine requires more compartments and more complex storage than a three-compartment layout.

Is it worth it?

Choose the Waterfly Running Belt Bum Bag if your priority is staying lightweight and stable: a 100g belt, an elastic waistband with a buckled closure, and a three-compartment setup that keeps your mobile and small essentials organised while you run. The lycra laminate and hand-washable approach also points to a practical, repeat-use accessory.

It may not be the best match if your phone/case setup doesn’t comfortably align with the main compartment’s sizing, or if you’re after deeper, heavier-duty storage for bigger gear. For most people using a phone, keys, and gels as the “run essentials”, it looks like a sensible, everyday runner’s option worth considering.