Dimensions for UNI 8181 Cross recessed countersunk (flat) head

d	b	k	d1
3	>= 0.6 x l	1.65	5.6
3.5	>= 0.6 x l	1.93	6.5
4	>= 0.6 x l	2.2	7.5
4.5	>= 0.6 x l	2.35	8.3
5	>= 0.6 x l	2.5	9.2
6	>= 0.6 x l	3	11