A 20 inch squeegee is best for larger designs up to 18" wide. Common uses for a squeegee this size are printing posters and signs. Please note, this squeegee will not fit in a 20" x 24" screen unless you turn it sideways.
choosing the right durometer...
60 durometer squeegees are the softest available, and is used for more delicate printing. A softer blade flexes more than a hard blade, and works best with thinner inks. 60 durometer squeegees also are great for high density printing since they allow a larger amount of ink to roll through the stencil.
70 durometer squeegees are a medium hardness, and are the most commonly used. A 70 durometer squeegee blade works well with almost any screen printing application, and is a great starter option for the beginning screen printer.
80 durometer squeegees are a fairly hard, and are great for working with plastisol inks. An 80 durometer screen printing squeegees are great for printing with thicker inks such as whites, yellows and other opaque plastisols.
90 durometer squeegees are the stiffest available and are great for more intricate print jobs. 90 durometer screen printing squeegees are commonly used with process printing where fine detail is a must.