According to DIN ISO 606 (ex DIN 8187).

Material: Special chain-steels. High-quality duplex roller chains, pre-stretched according to DIN. Waisted link plates (size 06 with straight link plates). Chains with an uneven number of links are supplied with inner links at both ends. Connecting links must be ordered separately. Temperature range: -20° to 120°C. Other temparatures possible with special lubricants.