It's labeled that way but what they mean is the weight of the trigger. I'd wager it's a 4, 4.5, 5, 5.5 lb springs which depending on the rest of the parts may or may not give you the advertised trigger pull weight. I"m sure it's a lighter pin safety spring and the trigger spring they don't say so it's stock or heavy.
I really don't like kits like this because they don't give you all the information and I think it's false advertising. They are trying to compete with lone wolf with a race to who has cheap crappy glock parts. The TTI kit I have used and trust. I order most of my springs from Wolff in packs because I use them and put them in friends guns when I do triggers.
My preferred Kit is a 4.5 striker spring, reduced pin safety spring and factory trigger return spring. Then I tune and polish the other parts to get the feel I want. The TTI kit is a good kit at a reasonable price.