Continuous temperature counts
Manufacturers like to quote peak temperature. Select on the continuous value: a sleeve rated 260 °C continuous tolerates more briefly, but not the other way round.
Spatter needs a coating
For weld spatter and casting sparks a coated version is required; untreated glass fibre absorbs molten metal and burns in. A silicone or aluminium coating lets the spatter slide off.
Leave air between sleeve and cable
A heat protection sleeve works thanks to the air layer around the cable. Choose one size larger than the cable diameter and do not pull the cuff tight.