This isn’t actually a custom Bric as such (although someone is welcome to create one), but it’s a sort of widget that you can add to a Blocs website through the Video Bric. It’s a fully responsive “before and after” image effect that can be customised just by adding your own images. You can check it out and download the widget from HERE. Although it’s been created in Temult Hype, you don’t need the application to customise it - just replace the two images files and add to your page.
One caveat - try and keep the image proportions as they are.