She's dinky, only about an inch higher (if that) in the shoulders than my collie sized woof. Looking to buy a car harness (tend to transport in the boot with dog bars mainly but I like to have the option available to use the backseats if needs be) and kong mainly - not sure if I'm better off going for the standard "greyhound" sizes of large, or should just risk the mediums on stuff (which is the size Layton takes). Like I say - I've never seen a dinkier little greyhound which makes it all a bit difficult shopping for her in advance of bringing her home. Coats I'll probably just get from the rescue anyway so I'll have her there with us - it's the other stuff that's harder to judge - particularly the harness and kong that I want to get ordered online since it's payday for hubby and I'm spending his money again muahahah.
Does the harness you want show measurements for girth etc or less usefull S/M/L? sighthounds tend to have deeper chests than average dog so not sure if it may work out larger than similar height dog or not. If you are able to transport her in the boot for time being perhaps order it once you get her, most things only take a few days to arrive,so probably less hassle than getting wrong size & having to return it. If its something PAH/Kennelgate type place sell they sometimes let you try it on the dog before you buy.
My whippets have medium sized harnesses and we did have a large for William when he was alive. I think Button would need a large too. She's about 26" at the shoulder so quite tall for a bitch. I bought mine from Lidhl when they had them in once and they fit them quite well. The only thing I found was that William was a big boy 31" to his shoulder and the strap that fastened into the seat belt clip wasn't long enough for him to stand up. Try measuring round her chest and take a tape measure with you to check it will fit.
I've got a bergan car harness that has a huge amount of adjustment in it. The seatbelt attachment also adjusts
I would take a mecurement of the waist and deepest part of her chest and go from there. Or get someone to measure for you.
In answer to it all - a collie-sized medium car harness fits her lovely! (She's THAT small and currently has missed her bed and zonked out on the floor bless her) Trying to measure her to get a coat made now - but she keeps on trying to go to sleep in the middle of it all - it's like trying to deal with that narcoleptic guy in Moulin Rouge!