This site has limited support for your browser. We recommend switching to Edge, Chrome, Safari, or Firefox.

K9 Booster Block


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

Customer Reviews

Based on 118 reviews
Richard Perkins
Fits the bill

The booster is just what our dog needed. Thanks

Danielle Williams
Happy Pupper

My dog loves going anywhere I go and since I already work over 40 hours a week the weekends are belonging to the dog so I take him on hiking on biking on my Vespa anywhere I go he goes and he loves being in his bright orange K9 backpack along with his name patch going down the side he's there a pie looking around being part of the adventure thank you so much for offering this amazing safe secure backpack that my little 9 lb dog can enjoy the world around him

Surella DaSilva
Toy Poodle Puppy

10wk old puppy is still quite small for us K9Sport Sack but I have no doubt that with the block he will be sitting pretty as he is snug and comfortable now with an added blanket at the bottom. We were able to keep him warm and take a nice walk at the park to get in some fresh air and socialization. I love the snugness of the pack for him and when I’m wearing it as well. All the straps and connections are well sewn excellent quality and stylish! You go Ezra!

Kim M.
A little needed boost!

Our Bleu is too short for the Medium but too thicc for the small. This booster solved the issue! It's super lightweight and supportive! Thank you for thinking of everything.

Andrea Lane
My Best Friend’s Best Accessory

I bought my K9 Sport Sack during the lockdown, and unfortunately the Booster Blocks were sold out. Originally I was stuffing a sleeping bag down in the bottom to boost my boy up enough to sit comfortably. My frenchie is barrel-chested and short, so the Large bag fits him width-wise but is too long for him. Two Booster Blocks later he sits comfortably in the sack for almost two hours our first time with the blocks. When you’re already spending good money on a bag, spend the extra to make it comfortable!! Highly recommend!