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.