This one fits a 10mm diamter low ESR capacitor. The one I used here has 1000 µF @25V and is 21 mm long.
See pictures for how to install... "Dry-fit" before soldering and solder everything together with the XT60 and capacitor halfway installed. Then slide the assembly into the final position. The part is long enough to allow you to fill the back of the XT60 with hotglue to provide insulation (not shown on the photo).