Review on WEBI Heavy Duty 90 Degree Stainless Steel Corner Brackets - 4Mm Thick, 6X6 Inches, Brush Nickel Finish - Ideal For Shelf, Wood, Furniture, And Shelves - Pack Of 4 by Jarrett Young

Purchased these solid angles to support a drawer front that was 19" taller than the drawer itself. It is important for my application that these angles be a true 90 degree in order for the drawer front to sit properly against the frame cabinet and not to introduce warping. As you can see from the photo that the angle was approx. 3/16 in 6" from being 90 degree. The angle is robust but I was able to correct it to 90 degrees (one for each side) with some persuasion. If mounted on a wall you should expect that the shelf will be tilted downwards (front to back)to a slight degree. So depending upon your application you will have to decide if a true 90 degree is essential or not, knowing that they are correctable. These are solid angles.