These genuine Volvo lockable lug nuts are designed to keep your wheels safe. The top of the lockable lug nut rotates- and is therefore very difficult to loosen without the included wrench. A solid connection between the wrench and the lug nut facilitates installation and removal- and eliminates the risk of the lug nut being tightened incorrectly.
These are as nice as any security wheel bolts could be. But the size of the hex head is 17 mm rather than 19 mm. Therefore your OEM plastic lug covers will not work. Volvo does sell a set of 4 lug bolt covers specifically for these security bolts...