These rules are the absolute best drafting tools I've ever seen. The 1/4" set is scaled for small items, like bra cup pieces! Set down your ruler to the right curve, remove the seam allowance in a since pass, then make your alterations. Then, put the ruler back on and add your seam allowance back to your pattern piece.
The 5/8" set is scaled for garment patterns, and can also be used for bras. The edge of the ruler is 5/8", but there are markings every 1/8" so that you can use it for any seam allowance under 5/8". Set your ruler down, mark your seam allowance, make alterations and put the seam allowance back on. Easily change seam allowances to enhance your sewing success.
Making pattern changes is easy with these rulers!