Features:
Material: 320C-Carbon Steel; 320A-Alloy Steel
Proof loaded at 2 times the Working Load Limit. Minimum Ultimate Load is 4 times the Working Load Limit.
Heat Treated.
There are signs such as Working Load Limit in the link.

Size(working  load  limit)		Main  dimensions(mm)				Weight(kg)
320C	320A	B	R	O	T
0.5t	0.75t	16	71	20.6	16.5	0.16
0.75t	1t	19	82	22.4	20.6	0.28
1t	1.5t	23	93	24.6	20.6	0.41
1.5t	2t	28	104	25.4	21.3	0.67
2t	3t	32	119	28.4	30.2	0.95
3t	4.5t	40	147	34.0	35.1	1.99
5t	7t	51	187	43.0	45.2	3.81
7.5t	11t	62	230	52.3	53.8	6.85
10t	15t	72	256	56.4	69.1	9.82