The 4th part of the Defender is a hard (and rather brittle-feeling) plastic 'holster' (Made in China, naturally!), which incorporates a belt clip. The cased phone clicks firmly into the holster, but I'd be wary of actually attaching the holster to a belt in case something snagged the phone, causing it to un-click and tumble out. However, I do use the holster as a screen-guard if I stuff the phone into a rucksack pocket.
Dimensions: 172mm x 83mm x 13mm (sides) or 15mm (top and bottom ends). Or, with holster fitted, max. 178mm x 90mm x 20mm (or 33mm including the belt clip). Weight of case with a Galaxy S20+ installed: 264g; or 328g including the holster.
Overall, an excellent product. However, whilst a price that was slightly above its rivals would be justified, its actual list price (which is 2-3 times the cost of most rivals) is highly questionable. Best shop around for a discounted price - as offered at MobileFun!