Boundary Supply Rennen MKII X-Pac vs Rains Backpack
The Boundary Supply Rennen MKII X-Pac is 18L and 0.85kg1.9lb; the Rains Backpack is 18L and 0.86kg1.9lb. The Boundary Supply Rennen MKII X-Pac is 0.01kg0lb lighter. The Rains Backpack costs $59 less. The Boundary Supply Rennen MKII X-Pac fits the carry-on limit of 36 of 36 major airlines and the Rains Backpack fits 36; under the seat, 7 and 0 of 26.
| Spec | Boundary Supply Rennen MKII X-Pac | Rains Backpack |
|---|---|---|
| Price | $199 | $140Best |
| Volume | 18L | 18L |
| Weight | 0.85kg1.9lbBest | 0.86kg1.9lb |
| Carry-on compliance | 100% | 100% |
| Personal-item compliance | 27%Best | 0% |
| Dimensions | 45×29×17.5cm17.5×11.5×7in | 50×30×12cm19.5×12×4.5in |
| Laptop | 16" | 16" |
| Compartments | n/a | 1 |
| Bottle pockets | 2 | n/a |
| Opening | wide coated zip opening, external laptop access | magnetic snap flap |
| Warranty | Lifetime | 2 years |
| Organizer | Yes | Yes |
| Shoe compartment | No | No |
| Hydration sleeve | No | No |
| Frame sheet | Yes | No |
| Water-resistant | No | Yes |
| Rain cover | No | No |
| MOLLE | No | No |
| Hip belt | No | No |
| Sternum strap | Yes | No |
| Load lifters | No | No |
| Shoulder strap | No | No |
| Luggage pass-through | No | No |
| Camera compartment | No | No |
| Material | PFAS-free Dimension-Polyant X-Pac ripstop, bluesign recycled interior | Rains signature waterproof PU-coated polyester (100% PES), 8,000 mm water column |
| Last checked | 2026-09 | 2026-09 |
Where their airline fit differs
| Airline | Limit | Boundary Supply Rennen MKII X-Pac | Rains Backpack |
|---|---|---|---|
| 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 |
| Frontier Airlines | Personal item | Fits | Too big |
| LATAM Airlines | Personal item | Fits | Too big |
| Volaris | 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.