Ultimate Guard Boulder sizes, decoded
Ultimate Guard's Boulder line runs 40+, 60+, 80+, 100+, and 133+, and the "+" numbers on the box are the double-sleeved rating. Ultimate Guard rates the 40+ for 40 double-sleeved cards, the 60+ for 60, the 80+ for 80, the 100+ for 100, and the 133+ for 133. But the 100+ is the size where that number stops being reliable: it measures the smallest interior depth of any Boulder, and real Dragon Shield Matte decks routinely fail to close in it.
The full lineup
Here's every Boulder size with its stated capacities and interior depth, straight from the manufacturer plus verified measurements where we have them.
| Box | Double-sleeved | Single-sleeved | Unsleeved | Interior depth |
|---|---|---|---|---|
| Boulder 40+ | 40 | 50 | 90 | not measured |
| Boulder 60+ | 60 | 80 | 140 | not measured |
| Boulder 80+ | 80 | 100 | 170 | 55mm |
| Boulder 100+ | 100 | 120 | 210 | 68.3mm |
| Boulder 133+ (Return to Earth) | 133 | 160 | not listed | not measured |
| Boulder'n'Tray 100+ | 100 | 120 | 210 | not measured |
The 80+ and 100+ are the only two sizes with a published interior depth, and the jump between them tells the story: going from 80 to 100 rated capacity only adds 13.3mm of depth. That's a tight margin for 20 more cards, especially once you add sleeves.
The double-sleeve gotcha
This is the part that trips people up. The Boulder 100+'s interior measures 68.3mm, one of the smallest depths of any box rated for 100 double-sleeved cards. Reviewers at Double Sleeved UK found it struggles specifically with Dragon Shield Matte sleeves, and a Dragon Shield Matte deck double-sleeved with KMC Perfect Fit inners has been reported as simply not fitting. Some players force it shut with heavy compression, but treat that combination as a no, not a maybe.
What does fit: 100 cards in KMC Hyper Mat outers with KMC Perfect Fit inners measures around 66mm, which is about 2mm of clearance inside the Boulder 100+. That all-KMC stack is the standard workaround people use to actually hit 100 in this box. Gamegenic Inner Sleeves paired with Gamegenic Matte Prime lands at 68mm, which is functionally zero clearance, essentially a coin flip depending on how the cards settle. Swap in a KMC Hyper Mat outer instead of the Gamegenic Matte Prime and you get more room (around 67mm). Gamegenic's Closable-style sleeves don't fit at all, per the same review.
If you're set on Dragon Shield Mattes for a double-sleeved 100-card Commander deck, the community's actual fix isn't a different brand of sleeve. It's sizing up. The Boulder 133+ is rated for 133 double-sleeved cards in Ultimate Guard's own sleeves, which leaves real slack when you're only putting 100 Dragon Shield-sleeved cards in it. That's the standard workaround, and it's a better bet than fighting the 100+'s lid.
Quick answers
Is the Boulder 100+ big enough for a double-sleeved Commander deck? It depends entirely on your sleeve stack. All-KMC combos fit with a couple millimeters to spare. Dragon Shield Matte combos are the ones that fail or come out extremely tight. Check your specific sleeves with the fit checker before you buy.
What's the difference between the Boulder 100+ and the Boulder'n'Tray 100+? Same rated capacities and the same 75mm exterior depth. The Tray version adds a taller body (136mm exterior height versus 98.5mm) to hold a card tray alongside the deck, not extra room for the deck itself.
Should I just buy the 133+ instead of the 100+? If you're running Dragon Shield Mattes double-sleeved and want a sure thing, yes. You lose nothing by having spare room, and the 133+'s rated 133-card capacity in Ultimate Guard sleeves means a 100-card Dragon Shield deck sits well inside its limits.
The Boulder line is a good deal for the price, but the 100+ is the one size in it that's earned its reputation as a coin flip. If your sleeves are anything other than a thin KMC stack, size up or check the numbers first.