How to choose case size & dimensions — B2B selection guide 2026

# How to choose case size & dimensions — B2B selection guide 2026 Choosing the right case size is the most important decision in B2B procurement: a too-small case won't fit equipment, a too-large case wastes foam, material, and shipping cost. This guide gives B2B buyers a systematic method. ## Key dimensions terminology - **Outer dimensions**: complete case including hinges, latches, handle (LxWxH) - **Inner dimensions**: usable space inside the case (LxWxH) - **Lid depth**: how far the lid inserts into the case when closed (typically 25-50mm) - **Base depth**: bottom half of the case, where equipment sits (typically 50-100mm) - **Total inner usable**: inner dimensions - lid depth (vertical) - **Effective inner**: inner dimensions - foam thickness (typically 10-20mm each wall) ## The 10% padding rule **Always size your case to be 10% larger than your equipment on each dimension.** Example: equipment 300×250×150mm - Minimum effective inner space: 330×275×165mm - Recommended case: 350×300×180mm or larger (more foam, more protection) This 10% padding gives: - 5mm foam on each wall (10mm total around perimeter) - Room for cable management, accessories, foam gaps - Tolerance for equipment manufacturing variances (±1-2mm per dimension) - Better shock absorption (more foam = more deceleration distance) ## Equipment measurement workflow ### Step 1: List your equipment - Each item: model, dimensions (L×W×H), weight, fragile areas - Accessories: cables, chargers, manuals, mountings - Foam-fitting: where connectors are, where foam should compress ### Step 2: Group by usage - Option A: All-in-one case (all equipment together) — bigger case - Option B: Modular cases (one per item) — multiple smaller cases - Option C: Hybrid (main + accessories) — 2 cases ### Step 3: Measure critical dimensions - For irregular equipment: measure in 3 axes - Add 5-10mm clearance for foam + handling - Round up to nearest 50mm (case standard sizes) - Check for height-with-handle (handle adds 30-50mm above equipment) ### Step 4: Verify clearance - Foam density: PE 18-30 kg/m³ compresses 10-15% under load - Equipment weight: heavier items need denser foam (less compression) - Connector clearance: 5-10mm minimum for plug access ## Standard case sizes (Kexin 6-series reference) | Model | Outer (mm) | Inner (mm) | Weight empty | Typical use | |-------|------------|------------|--------------|-------------| | 6-2010 | 215×165×95 | 190×140×75 | 0.4 kg | Compact electronics, GPS | | 6-2810 | 280×195×110 | 250×165×90 | 0.6 kg | DSLR body + lens | | 6-3618 | 365×265×185 | 335×235×155 | 1.1 kg | Camera + accessories | | 6-4020 | 410×305×195 | 380×275×170 | 1.4 kg | Multi-lens camera kit | | 6-5020 | 510×390×210 | 475×355×185 | 2.0 kg | Cinema camera + monitor | | 6-6030 | 600×430×300 | 565×395×270 | 2.8 kg | Drone + 4 batteries | | 6-7030 | 700×490×300 | 660×450×270 | 3.5 kg | Video equipment set | ## Common mistakes ### Mistake 1: Sizing to equipment exact dimensions Equipment at 298×248×148mm needs 350×300×180mm case (52mm extra on length). Buyers often pick 300×250×150mm case, then can't fit foam + 5mm clearance. ### Mistake 2: Ignoring handle/connector protrusion Equipment with cables attached may be 30-50mm taller. Always measure with all accessories attached. ### Mistake 3: Forgetting lid insert depth Lid takes 25-50mm vertical space. If lid is 30mm and base is 100mm, total internal is 130mm but usable is only 100mm tall. ### Mistake 4: Mixing units Sometimes specs are in inches (1 inch = 25.4mm). Kexin specifies mm. Always double-check. ### Mistake 5: Over-specifying Oversized case is heavier, more foam needed, more expensive to ship. Stick to smallest case that fits with 10% padding. ## OEM case size customization If standard sizes don't fit, Kexin offers: - 50mm increments (e.g. 450×350×200mm not available, but 500×350×200mm is) - Full custom: any L×W×H, MOQ 500 pieces, mold fee USD 3,000-8,000 - Hybrid: 6-series with 8-series depth (e.g. 6-5023 with 8-5023 internal layout) - 9-series HD: extra-deep for tall equipment Lead time: standard sizes 30-45 days, custom 60-90 days (mold production + sampling + production) ## Multi-case systems For 5+ pieces of equipment, consider modular: - 1 large case: bulk equipment (5-10 kg) — less efficient packaging, heavier case - 2-3 medium cases: by function (camera + lenses, audio + mics, drone + batteries) — better foam efficiency - Stackable design: cases stack on top of each other (saves pallet space) ## Sample data calculation Order 6-5020 case (510×390×210mm outer, 475×355×185mm inner): - Empty case weight: 2.0 kg - Add EPE foam (5mm each wall + 30mm base): ~0.4 kg - Add CNC foam insert (custom): ~0.6 kg - Total empty + foam: 3.0 kg - Equipment (e.g. ARRI Amira + 4 lenses): ~8 kg - Loaded weight: ~11 kg - Foam compression under 8kg load: 8% (PE 25 kg/m³) - Effective inner after compression: 460×345×170mm (still 10% padding for 400×310×155mm equipment) ## Weight vs dimensions trade-off For air freight, every 1kg added weight adds USD 3-5/case in shipping cost. For 1,000-piece order: - 5kg heavier case: USD 3,000-5,000 extra shipping - 5kg lighter case: same savings + easier handling - Choose smallest case that fits, with right foam ## Common B2B scenarios ### Scenario 1: Drone (DJI Matrice 350 RTK) - Equipment: 500×450×200mm (drone + RC + 2 batteries + cables) - Add 50mm clearance each side: 600×550×250mm - Standard case: 6-7030 (700×490×300mm outer, 660×450×270mm inner) - Or custom: 6-5023 extended (custom dimensions 600×500×250mm) ### Scenario 2: Cinema camera (ARRI Alexa Mini) - Equipment: 350×200×150mm (body) + 400×300×100mm (monitor + cables) - Combined: 400×350×200mm - Case: 6-5020 (475×355×185mm inner, lid takes 30mm → 155mm usable) - Need 6-5023 (475×355×230mm, 200mm usable) instead ### Scenario 3: Medical device (portable ultrasound) - Equipment: 400×350×80mm - Add 50mm: 450×400×130mm - Case: 6-4517 (450×355×170mm inner) ## Bottom line Apply the 10% padding rule, use Kexin standard sizes when possible, and add 5mm foam on each wall. For complex multi-equipment kits, contact Kexin engineering for free layout consultation.