Consider the following when selecting a size for your whelping box:

• The weight of the bitch
• The size of the bitch - for both weight and size, if you find that your bitch is on the larger end for what is expected of her breed, you may consider a whelping box one size larger for maximum comfort of both mom and puppies.
• Number of puppies in the litter - if you're expecting a large number of puppies, you may choose to get a box one size larger than what you would need with a small litter.
• Temperament of the bitch - if she's prone to jumping, you may consider getting a tall box  .  

Size Selection: Measure the rectangular space occupied by your bitch when she is lying down, fully stretched out. Add a few inches to each side for comfort. Remember to add an additional 4 inches on each side if you will be using rails.

Compare measurements to the size selection below. 

• EZclassic 28x28: 27.5" x 27.5" (outside 31" x 31" x 18")
• EZclassic 38x38: 38" x 38" (outside 41.5" x 41.5" x 18")
• EZclassic 38x38 TALL: 38" x 38" (outside 41.5" x 41.5" x 28")
• EZclassic 48x48: 48.5" x 48.5" (outside 52.25" x 52.25" x 18")
• EZclassic 48x48 TALL: 48.5" x 48.5" (outside 52.25" x 52.25" x 28")
• EZclassic 48x76 TALL: 48.5" x 77" (outside 52.25" x 80" x 28")