Medium 30mm (1.3/16 inch) White Nylon Non-Trace Hardwall Drywall Picture Hanger Hook - Pack of 50

Is is suitable for Victorian brick walls?

are these precisely 30mm top to bottom? bought ones that look the same from a different seller, and they were 32mm (though advertised at 30). thanks!

Is there a stated weight limit for these? I am aiming to hold about 5kg.