Shoulder Boulder/Chest Fly Attachment

- Ships By June 30, 2025
$274.99 USD

Build boulder shoulders & poppin’ pecs with this compact attachment.



Product Features

  • BUILD 3D DELTS

    Ditch the dumbbells and get more out of every rep! The smartly positioned weight horns increase tension at the bottom, where dumbbells fall short, targeting your delts more effectively. Perform lateral raises, single-arm front raises and rear delt flies to leave no delt undone on this full-shoulder solution!

  • UNLOCK CHEST FLIES

    On dumbbell chest flies, your biceps steal the show and pushing to failure feels more like gambling than training. But thanks to the Shoulder Boulder’s design, that sweet burn stays focused on your chest muscles. Plus, the 360° dial sets the ideal starting position AND acts as a safety catch—because your pecs deserve better odds than the roulette table.

  • COMPACT SHOULDER & CHEST STATION

    Why let a bulky machine take over your home gym? The Shoulder Boulder Lateral Raise Attachment mounts directly to your power rack and occupies a fraction of the footprint of a rear delt/chest-fly machine. This keeps your Castle of Gainz clutter-free; after all, the best gym is one you can actually walk through.

Product Details


Build boulder shoulders and poppin’ pecs for that iconic V-taper look!

Dumbbell shoulder and chest isolations suffer from inconsistent resistance, but the Shoulder Boulder’s design provides smooth, controlled movement with a superior resistance profile.

A standalone rear delt/chest fly station takes up a whopping 5-foot x 5-foot footprint (or more), while this rack attachment mounts to your rack to save space. Easily adjust its height on your power rack for the ideal fit.

This nifty unit uses weight plates, saving you money. Plus, easily micro-load the smaller muscles of your shoulders to minimize injury and get better gains!

While it doesn’t beat a cable machine for chest flies, the Shoulder Boulder comes in as a close second. Set it low & wheel over a bench (or mount a Seal Row Pad) for better chest flies that keep the tension exactly where it belongs: on your pecs.

Compatible with Hydra & Manticore racks. Also compatible with non-B.o.S. racks with a 3” width or length & ⅝” holes.

IMPORTANT: For user & equipment safety, ensure your rack or cable tower is bolted down or otherwise secured. Locking on your weight plates with collars is highly recommended.
Download The Shoulder Boulder Product Manual

PRODUCT SPECS



WARNING: Cancer and Reproductive Harm – www.P65Warnings.ca.gov
The Shoulder Boulder/Chest Fly Attachment by Bells of Steel is a sleek black mechanical device with two adjustable arms and a compact box labeled "BOS." It features multiple joints and knobs, making it perfect for achieving a V-taper look while balancing style and functionality.
Bells of Steel

Shoulder Boulder/Chest Fly Attachment

$274.99 USD

Build boulder shoulders and poppin’ pecs for that iconic V-taper look!

Dumbbell shoulder and chest isolations suffer from inconsistent resistance, but the Shoulder Boulder’s design provides smooth, controlled movement with a superior resistance profile.

A standalone rear delt/chest fly station takes up a whopping 5-foot x 5-foot footprint (or more), while this rack attachment mounts to your rack to save space. Easily adjust its height on your power rack for the ideal fit.

This nifty unit uses weight plates, saving you money. Plus, easily micro-load the smaller muscles of your shoulders to minimize injury and get better gains!

While it doesn’t beat a cable machine for chest flies, the Shoulder Boulder comes in as a close second. Set it low & wheel over a bench (or mount a Seal Row Pad) for better chest flies that keep the tension exactly where it belongs: on your pecs.

Compatible with Hydra & Manticore racks. Also compatible with non-B.o.S. racks with a 3” width or length & ⅝” holes.

IMPORTANT: For user & equipment safety, ensure your rack or cable tower is bolted down or otherwise secured. Locking on your weight plates with collars is highly recommended.
Download The Shoulder Boulder Product Manual

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