The following sizes are recommended, however this is only a recommendation. I don't know your dog.
3/16" - Show dogs - wraps once
1/4" - Show dogs, Pets with moderate hair - wraps once maybe twice
5/16" - Pets with thick hair - wraps twice maybe three times
3/8" - Pets with long, extra thick hair - wraps 3 times - great if you have a hard time using bands
5/8" - All Dogs - wraps 4 times - great if you have a hard time using bands
3/8" xtra hvy - for making dog bows, xtra thick topknots, Show dog wraps
Lightweight - puppies, dogs with fine hair
Latex - most commonly used, suitable for all hair, suitable for bows
Non Latex - slightly stretchier, suitable for all hair, not suitable for bows
These bands are perfect for dog groomers and pet owners.
Easy to use, won't break or matt with proper use. Please
match the size chart to your current bands. To Properly
measure, use a ruler to measure the inside dimension.
We have many people that purchase these for craft projects, however
these bands are for "putting up" or the making of topknots, and no claim
is made for other uses including making your own bows. Please be sure
as to size (see above), as once opened they cannot be returned. If you
Choose to purchase neon or non latex to make bows, use at your own risk.
To order 3/16”, 1/4”, 5/16”, 3/8” medium weight bands
Please note that large quantities (over 2500) in the US may require higher shipping, and you will
Be sent a paypal money request for additional shipping depending on location. Overseas
Will require an add’l fee over 1000 bands and an invoice will be billed for the balance.
5/8” comes in medium weight black,
cream chocolate, Neon and lightweight pastels (girls), colors (boys)
Less common sizes
1/4” latex lightweight
3/8” latex extra heavy
Neon 3/16”-3/8”
5/8” lightweight clear bands
3/8”-5/8” assortment
5/8” neon
5/8” chocolate & Black
3/8-5/8” boys lightweight
Assortment contains black,
Blue, tan, gray & white
3/8”-5/8” girls lightweight
Pastels contains pink, mint,
lavendar, peach etc
Boys lightweight

Facts about dog grooming bands: 

Only the amber colored are made from pure latex 

Clear and neon bands are now and always have been non latex.  

True latex cannot absorb color like rubber and plastic products so latex bands cannot be anything but amber colored.

See usage instructions on the topknot page
Latex Bands & Elastic Topknot Bands For Dog Bows, Dog Grooming and Pet owners.
Sample pack - 30 assorted bands
1/2” latex bands are super quality.
Nice heavy bands.
Latex dog grooming bands NEW
NEW Plum colored latex bands