Reddit mentions of Karlie Transport Box - in Accordance with IATA Requirements for Transportation of Live Animals

The first crate I bought was a wire crate that was much too large, and I ended up having to put in multiple boxes and dividers. My puppy was pretty bad with peeing in her crate during Weeks 8-12, so there was a lot of uncertainty on my part of whether she was "taking" to this crate.

So sometime around Week 13, I bought a plastic kennel-type crate. I wanted to know if she really didn't like the wire crate, and was soiling that as she wasn't viewing it as a 'home'. With the plastic kennel crate, I kept it in a separate room, and introduced it to her slowly.

Now in Week 16, her peeing has stabilised, and she sleeps just fine in the wire crate. So in the end, the plastic crate was largely unnecessary.

However, I will make a few points:

• Like you, I was wondering whether it was an issue with the puppy having negative association with the crate. But in my case, it wasn't. It was moreso a matter of her developing good bladder control. She still doesn't love the crate, like some dogs do, but I think that this is also a personality trait.
  
  
• It is still nevertheless useful to have multiple crates, especially one that is suited in size and can be carried. There are many instances where you need to confine puppy, and thus having a movable plastic kennel is useful. Is it worth the investment (£30)? I don't know. I wouldn't say I've gotten £30 out of it, but then again, I would probably hang on to it rather than reselling.
  
  
• As people point out, I don't think that it's a problem for your puppy to learn to love two crates. Sooner or later, your puppy will have to learn how to settle in different locations. For me, her wire crate has always been her 'nighttime' crate, and I may use the plastic one as a 'daytime' crate. I do not think this is a source of concern.
  
  I'll leave you with some advice:
  
  
• Be careful about getting a crate that is too large. I knew that my wire crate was too large when I bought it, as I was anticipating using the divider. However, even with the dividers, I found it too large, and I've had to fashion makeshift supplementary dividers. What I learned was that you may want to estimate the size based on the expected growth of the puppy, but don't extrapolate too much. You may simply want to buy a moderate crate that she might outgrow, rather than a large crate that she won't outgrow.
  
  
• This is the plastic crate that I bought and I think it works really well compared to wire crates. What I like about it is that it's extremely easy to clean and open up the top. You simply undo the latches on the side and lift out the top.