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K9 Sport Sack

K9 Booster Block


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Sizing your dog for a K9 Sport Sack® isn't an exact science. If your dog is in between sizes, has a wide body but short in length, or is still growing, the Booster Block fits snuggly in the bottom of your K9 Sport Sack to boost your dog up 3" (7.62 cm). It helps make the K9 Sport Sack experience more comfortable for you and your dog. 

  • Constructed of sturdy, quality foam
  • Removable, washable cloth cover
  • Use two blocks for a 6" lift
  • XS/S measures 3" tall * 8" wide * 5" deep (7.62 cm * 20.32 cm * 12.7 cm)
  • XS/S are interchangeable between XS and S sized backpacks
  • M/L measures 3" tall * 10" wide * 6" deep (7.62 cm * 25.4 cm * 15.24 cm)
  • M/L are interchangeable between M and L sized backpacks and are also compatible with XL and XXL if necessary
Shipping, Warranty & Returns


Domestic orders: A variety of UPS shipping methods are available. Please allow for 1-2 days of packaging before your item ships, 2-5 days if ordering a waterproofed or custom item.

International orders: UPS Worldwide Expedited shipping (average delivery in 3-5 days, but varies depending on location).

For more information regarding shipping click here.


We cover manufacturers defects and product malfunctions for the first 60 days (Excludes klearance and custom items). Learn more about our policy here.


If you end up with incorrect sizing don't worry! All size exchanges within 60 days are free excluding original shipping costs (Also excludes klearance and custom items). Learn more about our policy here.

Customer Reviews

Based on 111 reviews
Booster block for short doggies

I was using a folded up towel in the bottom on our size XS Sport Sack. The booster block helps Cricket fit better and helps her front paws stick through the armholes. She likes it a lot and she is a very sensitive rescue dog.
I use the backpack when we’re in the city, on hikes and even when I go to the grocery store.

Just what we needed!

This is just what we needed! Our dog is large but short lengthwise and we needed something to boost her up. Towels worked alright but the booster block provided her a firmer more stable service and she looked happier and more comfortable. Highly recommend if your dog is an awkward size and needs a few inches

Nelson W.
Size up with the booster block so the bag fits you!

My yorkie is only 7lbs and easily fits in the XS Air2 without a booster block. But keep in mind the smaller bag may be a tight fit for the handler, as it was for me. So, I opted for the size small Sport Sack with the booster block for a better fit for both of us. It’s nicely padded and also gives a 3” barrier from the bottom of the bag. Think of it as added protection and for your pups bum from getting cold. Highly recommend.

Marcus Laughlin
Finally in Stock

The medium/large fits perfectly into the K9 Sport Sack. Now if I can just get my Goldendoodle to learn to get inside the sack!

Just get it

If you have a small dog,senior dog, or a just want your fur baby to be comfortable when in this…get it. Those few inches that it gives helps with comfort for you and the pup. It gives them the option to sit like on the couch or in a seat.