Most all-in-one trainer racks from Major Fitness, Mikolo and RitFit use 2×2″ or 2×3″ uprights with 1″ holes, not the 3×3″ tube that most aftermarket rack attachments are built for. So 3×3″ brackets are out, while 2×2″ and 2×3″ parts with a 1″ pin are in play. Two other things vary more than buyers expect: hole spacing, which runs from about 2″ to 4.33″ depending on the model, and the cable ratio, which isn’t always 2:1. Start with your own brand’s attachments, then look at third-party parts sized for your exact upright.
Every spec below comes from Major Fitness’s, Mikolo’s, RitFit’s and the attachment makers’ own pages, checked October 17, 2026.
Disclosure: links marked “affiliate” go to Bulletproof Fitness Equipment or Exponent Edge, whose affiliate programs Hypertrophy Protocol is in. If you buy through them, Hypertrophy Protocol may earn a commission at no extra cost to you. Links marked “referral” go to Beyond Power, which has no affiliate program; buying through them may earn Hypertrophy Protocol referral credit.
All-in-one trainer specs that decide fit
| Model | Uprights | Holes | Hole spacing | Cable ratio | Weight stack |
|---|---|---|---|---|---|
| Major Fitness F22 | 2×3″, 14-gauge | 1.02″ | 3.94″ | 2:1 | None listed |
| Major Fitness F22 Pro | 2×3″ (12-gauge front, 14-gauge rear) | 1.02″ | 1.97″ | 2:1 | Dual 170 lb |
| Major Fitness F35 / F35 Pro | 2×3″ (12-gauge front on the Pro) | 1.02″ | 3.94″ / 1.97″ (Pro) | 1:1 | Pro: 100 lb per side |
| Major Fitness B52 / B52 Pro and EVO | 2×3″; Pro and EVO add 2×2″ middle uprights | 1.02″ | 3.94″ / 1.97″ (Pro, EVO) | 2:1 | 170 lb on Pro and EVO; add-on for the standard B52 |
| Mikolo F4 / F4-Elite | 2×2″, 14-gauge | 1″ | 2″ | 1:1 | F4 plate-loaded; F4-Elite 110 lb |
| Mikolo M4-2.0 | 2×2″, 14-gauge | 1″ | 2″ | 2:1 | Elite: 132 lb per side; Ultra plate-loaded |
| Mikolo K3 | 2×3″, 14-gauge | 1″ | 4″ | 2:1 | Not stated |
| RitFit P3 | 2×2″, 14-gauge | 1″ | Not stated | 2:1 | Plate-loaded |
| RitFit P9 | 2×2″ (50 x 50 x 1.8 mm), 14-gauge | 1″ | 4.33″ | 2:1 single cable, 1:1 dual | 198 lb (99 lb per side) |
| RitFit M1 PRO | 2×2″, 14-gauge | 1″ | 4.33″ | 2:1 high and low | Optional 264 lb stack |
Not every Mikolo rack follows this pattern. The Mikolo P5 is a conventional power rack with 3×3″ uprights and 1″ holes 2″ on center (Mikolo lists 14-gauge on the product page and 11-gauge on its package overview), and it has no cable system. Mikolo also lists the K7-ULTRA as 2×3″ 14-gauge with a 1:1 cable ratio, but doesn’t publish its hole size or spacing.
Why 3×3″ attachments don’t fit
A bracket built to wrap a 3×3″ upright is 76.2 mm across inside. A 2×2″ upright is 50.8 mm, which leaves a 25.4 mm gap: far too much play for anything that carries load, even when the 1″ pin lines up. A 2×3″ upright matches on its 3″ face only, which is why Exponent Edge says the 2×3″ version of its Infinity Arm “will only attach on the 3-inch side.” Power rack upright sizes explains the tube classes in more detail.
Major Fitness lists 1.02″ holes, so 1″ pins pass through. The tube is the problem, not the pin.
Hole spacing is the hidden trap
Single-pin parts like a J-hook or a band peg only need one hole. Anything with two pins, or a bracket that spans several holes, needs your rack’s spacing:
- Major Fitness Pro models list 1.97″ spacing, and the standard F22, F35 and B52 list 3.94″. Those are close to 2″ and 4″ but not equal. Across three 1.97″ steps, the gap against a 2″-pitch part adds up to about 0.09″, which can be enough to bind a bracket that spans several holes.
- Mikolo’s F4 and M4-2.0 use 2″ spacing, the same pitch as many full-size racks.
- Mikolo’s K3 uses 4″. A part built for 2″ spacing only lines up if its pins sit a multiple of 4″ apart.
- RitFit’s P9 and M1 PRO use 4.33″, which works out to about 110 mm and doesn’t line up with any imperial pitch beyond a single hole.
Also check whether your trainer’s cable carriages run on the same uprights you want to hang attachments on. A bracket that blocks the carriage’s travel costs you part of the cable system. The rack attachment compatibility checklist walks through pin count and spacing step by step.
What does fit
Your own brand’s attachments first. Mikolo says the F4 and F4-Elite work with “a wide range of 2×2 attachments,” with “no adapters needed.” Major Fitness says “all our old 2×3″ attachments will work on the F22 Pro.” RitFit describes the M1 PRO’s add-ons as a closed set of parts it lists for that machine.
Third-party parts sized for 2×2″ or 2×3″ uprights:
| Attachment | What the maker lists | On an all-in-one trainer |
|---|---|---|
| Exponent Edge Infinity Arm 2.0 (affiliate) | Fits 3×3″ racks and 2×3″ racks “(will only attach on the 3-inch side)”; optional UHMW adapter for 2×2″; “This Rack Will not fit on a Major Fitness B52 Model” | Possible on 2×3″ or, with the adapter, 2×2″ uprights; not the B52. No Mikolo or RitFit model is named |
| Bulletproof ISOLATOR 2×2/2×3 (affiliate) | A separate ISOLATOR carriage for 2×2″ and 2×3″ posts with a 1″ pin hole; its adapter plates are “Not compatible with 3×3 post sizes” | Sized for these uprights; no all-in-one brand is named |
| Bulletproof VTS Lite HOME (affiliate) | “Off-the-shelf rollers seamlessly fit 3×3, 2×3, and 2×2 uprights” | Check inside width, and whether cable carriages share the uprights |
| Beyond Power Adaptive Bar Mount (VOLTRA I) (referral) | Clamps a “0.6”-2″ (16 mm-51 mm) diameter bar” | Mounts to a pull-up bar or round bar instead of the upright holes |
| Beyond Power Adaptive Rack Mount (VOLTRA I) (referral) | Uprights up to 4″ (102 mm); reversible pin for 5/8″ or 1″ holes | Size range, not a named rack list |
Beyond Power’s Strap Mount is the exception: it lists a minimum post size of 3.15″ round or 2.76″ square, which is bigger than a 2×2″ upright and the 2″ face of a 2×3″. The Beyond Power VOLTRA guide covers all four mounts. Before you order anything, check your exact model in the Rack Attachment Fit Checker.
Not every all-in-one is 2:1
The Major Fitness F22 and B52, Mikolo’s M4-2.0 and K3 and RitFit’s P3 and M1 PRO list 2:1. The Major Fitness F35, Mikolo’s F4 and F4-Elite and the K7-ULTRA list 1:1. RitFit’s P9 runs 2:1 on one cable and 1:1 with both. Mikolo’s Falcon 2.0 functional trainer is listed inconsistently: its spec table says 2:1 and its title says 1:1 and 2:1.
At 2:1 you feel about half the plate or stack weight and the handle travels twice as far. For example, two horns on one 2:1 carriage, each holding two 45 lb plates, add 180 lb of plates, which works out to about 90 lb at the handle before carriage weight and friction. Thinner plates fit more on a horn, but they don’t raise the machine’s rated capacity. The cable pulley ratio calculator works out what you feel, and cable pulley ratios explained covers why. Before adding weight past the top of a stack, read weight stack pin extenders and adapters.
Before you order
- Confirm your upright size. 2×2″ and 2×3″ parts aren’t interchangeable, and some Major Fitness Pro models mix both.
- Check your hole spacing for any attachment with more than one pin.
- Keep the cable carriages clear of anything you mount on the uprights.
- Read the exclusions. Exponent Edge rules out the B52 by name.
- Know your ratio before you compare loads with another machine.
For handles and attachments that clip to the cable instead of the frame, see cable attachments for hypertrophy. If you’re still choosing between plate-loaded and stack machines, plate-loaded vs weight stack cable machines compares them, and the Power Rack Comparison Tool lines up all-in-one trainers against standard 3×3″ racks.
To see how your trainer’s uprights compare with a standard 3×3″ 11-gauge rack, enter both in the Upright Stiffness Calculator.
The verdict
On a Major Fitness, Mikolo or RitFit all-in-one trainer, skip 3×3″ attachments and start with your own brand’s parts. For third-party additions, buy the 2×2″ or 2×3″ version with a 1″ pin, check your hole spacing for any two-pin part, and keep the cable carriages clear. The Infinity Arm 2.0, the ISOLATOR 2×2/2×3 and the VTS Lite HOME are sized for these uprights, but none of their makers names a specific all-in-one model as a confirmed fit, and Exponent Edge rules out the B52.
Specifications checked against manufacturer pages on October 17, 2026. Manufacturers change specs; confirm on the product page before ordering.