METAL Nickel plated steel Continuous Loop (Never-ending) chain Fits the 25mm, 28mm, 32mm, 40mm and the 45mm Roller sizes. And Roman Blinds. Please read below. Chains are sold by the Chain HANGING DROP size. From the sidewinder to the bottom of the hanging chain. So a 1m hanging drop chain would measure 2m in length if you cut it in half. NOT THE BLIND DROP The length from the sidewinder to the bottom of the hanging chain. NOT the CIRCUMFERENCE Choose your correct hanging drop from the drop-down box above Beaded Control Chain (operating chains) These chains are commonly found on vertical, roller and roman blinds, please check the size of your existing chain before ordering Number 10 chain - 4.5mm ball diameter, 2mm gap, approx 6 balls per 30mm, 17 balls per 100mm) NB Control chains should always be fitted with a safety device to avoid strangulation- each chain is supplied with a FREE safety device. Please see this link for advice https://www.makeitsafe.org.uk/wp-content/uploads/2016/10/Surveyor-Installer-Guide-for-Trade.pdf