What does - ていっすよ。mean? How do I use it?

[Kurokome]

I'm practicing Japanese by reading manga but I came across this verb form.

Does anyone know what it means? Is it colloquial or?

The context is that:

化粧水なら俺の使っていっすよ？

How can I use it in sentences?

 

[nekojita]

It's a colloquial form of ~ていいです

 

[undrentide]

使っていっすよ ＜ 使っていいですよ (You may/can use it.)
いいっす or いっす is colloquial contraction for いいです。