What size crate would a Weimaraner need?

I'd go extra large… Because they are big dogs.
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large would be good,but if she is already potty trained then get an extra large for more room
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Considering the size of the dog, extra large.
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A large one, I forgot the exact dimensions ours have.
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large but you should ask your vet just call them its free
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36 inches front to back, 24 or so inches wide, height of 24-27" if possible. While you can get larger, this is adequate for any female Weims to turn around in.

I recommend wire crates, as some dogs HATE the plastic, they can't see out of. The wire can be draped with a trap or beach towel, if she needs a more sheltered crate. Wire also provide better ventilation. I prefer the Gorilla-tough (Foster & Smith) or Kennel-aire crates (more escape-proof) for Weims.

If she hasn't been crate-trained you need to do this is stages, not all at once. (It would seem to me if she were crate-trained, they'd also give you her crate.) I hope you got her dog bed & whatever food she is on, & her vet records… or the name of her vet. Have them sign over the registration papers (if she has any) or sign a simple form, saying they turn ownership over to you. (You don't want them claiming you stole the dog.) I do Weim Rescue, we handle this sort of occurrence, all the time.
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25 years of Weim ownership, 14 yrs, being the Rescue Chairman for my Weimaraner club. BTW, unless you really want the dog, you can turn her over to Weim Rescue. (They won't put her down.) She will be carefuly fostered & placed after being spayed, updated on her shots & checked for heartworms.
WCA rescue (contact any local club - most do rescue)
http://www.weimclubamerica.org/about/alphaclubs.html
Adoption advice:
http://www.whole-dog-journal.com/issues/9_1/features/Dog-Adoption-Advice_15779-1.html
http://www.canismajor.com/dog/preown.html
http://dogtime.com/discussion/forums/2/topics/1521