Several Avery name badge insert sheets are 8 per sheet, 2-1/4x3-1/2 inches. The different numbers represent different pack sizes or printer compatibility (inkjet or laser or both), but they all share the same template. Note that the templates for name badges that are a different size are different.
You can design these using the 5390 template in Avery Design & Print Online.
You can also use a template built into Microsoft Word or download an Avery 5390 template for Word, Photoshop, Illustrator, InDesign or Pages.
Here's some information on recommended printer settings.
If you want more information about a specific Avery product, search for the product number on avery.com.