A 3C accessories seller called me last week. He blocked air space to Saudi at RMB 28/kg in late October, four yuan cheaper than loose cargo. Then his agent in Riyadh billed him for "minimum chargeable weight." He paid an extra RMB 17,000 on one shipment. Blocked space is not a ticket. It is a commitment.
The most common trap is the minimum chargeable weight. Say you block 1,000 kg a week but only ship 600 kg. The remaining 400 kg gets charged as "dead air." In peak season, sellers overestimate sales. My rule: sign your first block at 70% of forecast, leave 30% for loose cargo.
Ask about destination charges before signing. At Riyadh airport, deconsolidation, storage and document fees can differ by 30% between agents. Some cheap block rates hide costs there. A RMB 26/kg block can end up dearer than RMB 28/kg loose cargo.
Another detail: volumetric rules. 3C accessories are bulky. If the agent uses 1:6000, your real cost jumps. Get the volumetric divisor and minimum volumetric weight in writing. I know Saudi lanes often use 1:6000; some UAE lanes use 1:5000.
Capacity will only tighten before White Friday in November. Frankly, blocked space suits established sellers with stable volume and few SKUs. New sellers should stick to loose cargo. Do not save RMB 3/kg and sit on stock. At 8ship, we break down destination fees before quoting. Have you actually calculated the dead-air cost in your block contract?