Man wearing black CORE Duffel over shoulder in gym, with American Flag in background
Man carrying black CORE Duffel in gym
Black CORE Duffel with green lifting belt inside sleeve, held in women's hand, inside dark gym
Black CORE Duffel sitting on wooden box
Side profile of Black CORE duffel with matching weight lifting belt attached
360* views of black CORE Duffel
Front view of black CORE Duffel sitting on wooden box
Flat lay of black CORE duffel with gym essentials
Birds eye view of black CORE Duffel packed with KINGKONG hoodie, KNKG green lifting belt, skipping rope, iPad and workout accessories
Divider organization system packed inside black CORE Duffel
Birds eye view of empty black CORE Duffel, showing internal pockets and compartments
NOBULL sneakers inside black CORE Duffel shoe compartment
KNKG Drink bottle and Blender Shaker Bottle packed inside black CORE Duffel bottle pockets
Close up of KNKG zippers and metal buckles on black CORE Duffel
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Medium and large CORE Duffel stacked on top of each other, showing size difference
Side by side of large and medium CORE Duffel showing size difference

CORE Duffel Medium 35L

4.8
Rated 4.8 out of 5 stars
4.8 Stars (807 Reviews)
$169.95
Size: Medium 35L
Mini 15L
Mini 15L
Medium 35L
Medium 35L
Large 51L
Large 51L
Color: Black
Black
Black
Natty
Natty
Green
Green
Desert
Desert
Limited Edition - Waxed Canvas:
Camo
Camo
Traditional
Traditional
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OUR BEST SELLING GYM DUFFEL WITH LIFTING BELT ATTACHMENT

  • External weightlifting belt attachment
  • 13/15” Internal laptop sleeve
  • Sealed internal shoe compartment
  • Dual bottle pockets 

Do you even lift? If so, meet your new favorite lifting partner. Say goodbye to your belt taking up precious space in your bag, with this unique and specially designed lifting belt attachment that ensures functionality isn’t compromised whatsoever. The CORE Duffel is made to store everything you need and support you every time you step into the gym.

(Lifting belt sold separately)

Covered by our promise to be free of defects in material or workmanship within its practical lifetime. If there is a defect in materials or workmanship KNKG will repair or replace your bag, including free shipping.

Our bags are meticulously designed to stand up to the test of time. We utilize durable materials, coupled with top-notch craftsmanship and rigorous testing, resulting in the toughest bags in the game. You can confidently pack your bag to its maximum capacity without worrying about it stretching or tearing.

The CORE Duffel is made from:

  • 500D nylon body material (PVC backing)
  • YKK zippers
  • Powder-coated steel buckles
  • Ripstop nylon lining
  • Nylon webbing
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CORE DUFFEL
SIZE COMPARISON
Capacity
Bag Weight
Height (H)
Width (W)
Depth (D)
Shoe Storage
Laptop Sleeve
Lifting Belt Size
MINI
15 L / 4 GAL
0.6 kg / 1.3 lbs
23cm / 9.1"
38cm / 15"
18cm / 7.1"
Not recommended
iPad
KNKG Belt
MEDIUM
35 L / 9.2 GAL
0.8 kg / 1.8 lbs
28cm / 11"
45cm / 17.7"
28cm / 11"
Size 10
Up to 13"
6.3" (W) - 45.7" (L)
LARGE
51 L / 13.4 GAL
1 kg / 2.2 lbs
32cm / 12.6"
50.8cm / 20"
32cm / 12.6"
Size 13
Up to 15"
6.7" (W) - 51.5" (L)
Capacity
Bag Weight
Height (H)
Width (W)
Depth (D)
Shoe Storage
Laptop Sleeve
Lifting Belt Size
MINI
15 L / 3.96 GAL
0.6 kg / 1.3 lbs
23cm / 9.1"
38cm / 15"
18cm / 7.1"
Not recommended
iPad
KNKG Belt
MEDIUM
35 L / 9.2 GAL
0.8 kg / 1.8 lbs
28cm / 11"
45cm / 17.7"
28cm / 11"
Size 10
Up to 13"
6.3" (W) - 45.7" (L)
LARGE
51 L / 13.4 GAL
1 kg / 2.2 lbs
32cm / 12.6"
50.8cm / 20"
32cm / 12.6"
Size 13
Up to 15"
6.7" (W) - 51.5" (L)

Workouts are tough but these bags are tougher. Effortless to carry and palpably robust. This thing does it all and measures in at the perfect size.

Designed for serious lifters who crave serious organization.

This is the best gym bag for powerlifters. Many amazing features that set this bag apart from its rivals. The outer material is tough, durable, and lightweight while also being water resistant and easy to clean.

FAQS

The main difference is the unique weightlifting belt attachment. This feature allows the bag be used as normal, while carrying a cumbersome lifting belt on the outside. Other changes are the volume (35L) and the layout.

Most of the materials are the same as used in other KNKG bags. YKK zippers, heavy duty buckles, nylon lining and webbing are all the same. In the CORE range, we have gone for a lighter 500D nylon outside and a new velcro logo feature that allows you to go 'incognito' with your own patches.

Measure the widest point of your belt and its length.

The CORE35 (medium) duffel can fit a belt up to 6.3"/16cm wide and 45.7"/116cm long.
The CORE51 (large) duffel can fit a belt up to 6.7"/17cm wide and 45.7"/116cm long.

A lever belt can fit, but you should count the lever into your measurement.

The CORE35 (Medium) will fit size 10 shoes. The CORE51 (Large) will fit size 13 shoes. Larger shoe sizes will fit our PLUS Duffel.
4.8
Rated 4.8 out of 5 stars
Based on 807 reviews
Total 5 star reviews: 704 Total 4 star reviews: 81 Total 3 star reviews: 8 Total 2 star reviews: 3 Total 1 star reviews: 11
97%would recommend these products
Slide 1 selected
807 reviews
  • PG
    Patrick G.
    Verified Buyer
    Reviewing
    CORE Duffel Mini 15L
    I recommend this product
    What type of training is your KNKG bag supporting you with? Weightlifting, Functional Circuit Training
    Using For: Gym Bag
    Rated 5 out of 5 stars
    Perfect bag for most of my workouts

    I had been looking around for a small duffel for the gym for the last couple of months and I randomly decided to look here again. I already own a King Kong duffel that I really liked but didn't need so much room anymore so when I found there was a 15L duffel from them I jumped on it immediately. It has just the right amount of space for what I need for 90% of my workouts (I only use my other one on days I do heavy cardio and need extra clothes) and is small enough to easily carry around with me in the gym. The zippers are really nice and I love all the compartments. I only wish there was a bottle sleeve on the outside because I'm worried about it exploding inside the main compartment, but otherwise the bag is perfect.

    Was this helpful?
  • LT
    Lawrence T.
    Verified Buyer
    Reviewing
    CORE Duffel Medium 35L
    I recommend this product
    What type of training is your KNKG bag supporting you with? Weightlifting, CrossFit
    Using For: Gym Bag, Sport / Fitness
    Rated 5 out of 5 stars
    Love this bag

    Well designed, thought of everything, the last gym bag you’ll purchase.

    Was this helpful?
  • KW
    Kyle W.
    Verified Buyer
    Reviewing
    CORE Duffel Large 51L
    I recommend this product
    What type of training is your KNKG bag supporting you with? Weightlifting, CrossFit, Olympic Lifting
    Using For: Gym Bag, Sport / Fitness
    Rated 5 out of 5 stars
    Overdue

    I should have purchased this bag a long time ago. I have been going to a gym and competitions for many years and never spent the money for a nice gym bag. Instead, I suffered through losing equipment or not able to find it when I needed it. This bag is compact, sturdy, organized and I will never need to replace it due to its high quality. Highly recommend! I got the organizer too and have it organized with neoprene and towels in large compartment; grips, straps, wraps and headbands in middle; jump ropes and a clean set of clothes in last compartment. It also hold my size 12 lifters neatly while standing tall.

    Was this helpful?
  • DP
    Dominique P.
    Verified Buyer
    Reviewing
    CORE Duffel Mini 15L
    I recommend this product
    What type of training is your KNKG bag supporting you with? Fight & Combat Sports
    Using For: Every Day Carry
    Rated 5 out of 5 stars
    Great product

    Great bag for the price

    Was this helpful?
  • K
    Khalid
    Reviewing
    CORE Duffel Mini 15L
    I recommend this product
    Rated 5 out of 5 stars
    5 Stars

    Awesome quality. Very satisfied with my purchase!!!

    Was this helpful?
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Ultimate Gym Bag with Weightlifting Belt Attachment — KNKG CORE Duffel

Built for serious lifters, the CORE Duffel is the gym bag that solves one of the biggest packing problems: cramming your lifting belt inside your bag. With its iconic external belt attachment, this duffel keeps your belt secure on the outside, saving precious space inside for the gear that matters.

Why the Weightlifting Belt Attachment Matters

Most gym bags weren’t built for people who take their weightlifting serious. Stuffing a thick lifting belt inside a bag means less room for everything else, and more time sifting around inside your bag. The CORE Duffel changes that with an external weightlifting belt sleeve designed specifically for heavy training gear:

  • Save Space: Carry your belt outside and keep the interior free for other gear.
  • Secure Fit: Reinforced straps hold your belt firmly in place, no slipping or sagging.
  • Quick Access: Grab your belt instantly without digging through your bag mid-session.
  • Proven by Lifters: Tested by athletes who lift heavy and pack large.

What Fits Inside

The CORE Duffel isn’t an everyday commuter bag — it’s designed for the gym. The interior and compartments give you space for everything you need for training:

  • Weightlifting shoes or sneakers (dedicated shoe compartment)
  • Change of clothes
  • Shaker bottle or water bottle (dual external bottle pockets)
  • Chalk container
  • Knee sleeves, wrist wraps, straps
  • Lifting accessories (grips, straps, bands)
  • Towel
  • Headphones or gym electronics
  • Snacks or post-workout supplements
  • Phone, wallet, and keys (secure valuables pocket)

With your lifting belt attached on the outside, the CORE Duffel has more interior space to comfortably fit everything else you need for a serious training session.

Materials & Build

Like every KNKG bag, the CORE Duffel is built to take a beating. From heavy training sessions to being tossed in the trunk or dropped on the gym floor, it’s designed to last. Reinforced stitching, abrasion-resistant fabrics, and quality hardware mean this bag doesn’t just survive hard use — it thrives on it.

  • 500D nylon body material with PVC backing
  • Ripstop nylon lining
  • Heavy-duty YKK zippers
  • Reinforced nylon webbing straps and handles

Why Choose the CORE Duffel?

  • Famous and trusted external weightlifting belt attachment
  • Purpose-built for lifters — not for everyday commuters, built for gym rats who take their training seriously
  • Smart compartments: shoe storage, dual bottle pockets, valuables pocket
  • Premium materials built to handle heavy training loads
  • The gym bag that keeps your belt secure and your gear organized