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Shoulder Boulder/Chest Fly Attachment

- Ships By October 13, 2025
5.0
Rated 5.0 out of 5 stars
2 Reviews
$324.99 CAD

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

Shoulder Boulder/Chest Fly 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.

PRODUCT SPECS

5.0
Rated 5.0 out of 5 stars
Based on 2 reviews
Total 5 star reviews: 2 Total 4 star reviews: 0 Total 3 star reviews: 0 Total 2 star reviews: 0 Total 1 star reviews: 0
100%would recommend this product
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2 reviews
  • MV
    Michael V.
    Verified Buyer
    I recommend this product
    Rated 5 out of 5 stars
    Yesterday
    Amazing

    Just got my Boulder Shoulder attachment in, well worth the 5 month wait. I originally bought, and still have, another lateral raise attachment from another company and it did the job but very basic, can only do lateral raises and maybe bent over rear delts. This new one from BoS is the REAL DEAL, belive that. The handle position is better, you get a far greater feel for the movement plus you can do standing chest work, flat bench or incline flyes and if you have something like the BoS seal row pad your rear delts will both hate you and thank you. Glad I ordered this pre tariffs and even if I had to but it today it's still well worth the investment. I've got a small handful of things from BoS from my plate loaded lat pulldown, belt squat, short back FID bench and pieces of their Manticore rack which I added to my existing Titan rack and so far I'm beyond pleased. Every item came in perfect condition and works excellent, beyond what I initially expected. You can't go wrong with this one...another home run from the Bells.

    Was this helpful?
    Bells of Steel Canada
    Yesterday

    Thanks a bunch for the glowing review, Michael! We're pumped that the Boulder Shoulder/Chest Fly Attachment has exceeded your expectations — it sounds like it's become a true game-changer in your setup! Hitting those rear delts, nailing those chest flyes, and improving the feel of every movement? That's music to our dumbbell-clad ears! We're thrilled our gear has you beyond pleased, and we're here anytime your gym needs another boost.
    Yours in strength,
    The B.o.S. Crew.

  • AC
    Andrew C.
    Verified Buyer
    I recommend this product
    Rated 5 out of 5 stars
    4 months ago
    Love it!

    Another great product by BOS! I have been looking for something like this forever. Dont stop innovating!

    Was this helpful?
    Bells of Steel Canada
    4 months ago

    Thanks so much for the incredible feedback, Andrew C! We're absolutely stoked to hear you're loving your new Shoulder Boulder/Chest Fly Attachment. It's fantastic to know we've created something you've been searching for - that's exactly what drives us to keep pushing the boundaries with our equipment designs. Your enthusiasm really means a lot to us!

    Yours in strength,
    The B.o.S. Crew
The Bells of Steel Shoulder Boulder/Chest Fly Attachment is a black mechanical device with adjustable arms and knobs, ideal for chest fly exercises to build the Shoulder Boulder look.
Bells of Steel

Shoulder Boulder/Chest Fly Attachment

$324.99 CAD

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.

Shoulder Boulder/Chest Fly Attachment

  • Hydra (3" x 3"; 5/8" Holes)
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  • $199 MAX SHIPPING

  • PROUDLY CANADIAN SINCE 2010

  • EXCELLENT WARRANTY