Billykirk No. 609 Standard Issue Backpack Tote vs Mountainsmith Zerk 13 UL Daypack
The Billykirk No. 609 Standard Issue Backpack Tote is 12.6L and 0.82kg1.8lb; the Mountainsmith Zerk 13 UL Daypack is 13L and 0.82kg1.8lb. They weigh the same. The Mountainsmith Zerk 13 UL Daypack costs $115.05000000000001 less. The Billykirk No. 609 Standard Issue Backpack Tote fits the carry-on limit of 36 of 36 major airlines and the Mountainsmith Zerk 13 UL Daypack fits 36; under the seat, 10 and 1 of 26.
| Spec | Billykirk No. 609 Standard Issue Backpack Tote | Mountainsmith Zerk 13 UL Daypack |
|---|---|---|
| Price | $280 | $164.95Best |
| Volume | 12.6L | 13L |
| Weight | 0.82kg1.8lb | 0.82kg1.8lb |
| Carry-on compliance | 100% | 100% |
| Personal-item compliance | 38%Best | 4% |
| Dimensions | 40.6×30.5×10.2cm16×12×4in | 45.7×22.9×12.7cm18×9×5in |
| Laptop | 15" | no laptop sleeve |
| Bottle pockets | n/a | 2 |
| Opening | n/a | Panel access, Panel loader main compartment |
| Warranty | 5 years | Lifetime |
| Torso length | n/a | 38.1 to 48.3cm (15 to 19in) |
| Organizer | Yes | Yes |
| Shoe compartment | No | No |
| Hydration sleeve | No | Yes |
| Frame sheet | No | Yes |
| Water-resistant | No | No |
| Rain cover | No | No |
| MOLLE | No | No |
| Hip belt | No | Yes |
| Sternum strap | No | Yes |
| Load lifters | No | No |
| Shoulder strap | No | No |
| Luggage pass-through | No | No |
| Camera compartment | No | No |
| Bike-ready | No | No |
| Material | 10.10 oz waxed canvas, premium vegetable tanned leather, 1 in nylon tubular webbing handle, matte nickel-plated brass hardware | 100D and 210D ROBIC nylon X-Grid ripstop (UHMWPE) with UTS coating, 150D polyester liner |
| Last checked | 2026-10 | 2026-09 |
Where their airline fit differs
| Airline | Limit | Billykirk No. 609 Standard Issue Backpack Tote | Mountainsmith Zerk 13 UL Daypack |
|---|---|---|---|
| Air Canada | Personal item | Fits | Too big |
| Allegiant Air | Personal item | Fits | Too big |
| American Airlines | Personal item | Fits | Too big |
| British Airways | Personal item | Fits | Too big |
| easyJet | Personal item | Fits | Too big |
| JetBlue Airways | Personal item | Fits | Too big |
| LATAM Airlines | Personal item | Fits | Too big |
| Volaris | Personal item | Fits | Too big |
| WestJet | Personal item | Fits | Too big |
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Specs come from each brand's own product page. Fit uses listed dimensions in any orientation. How we score carry-on fit.