Read width, girth and usable length
Compare the same measurements across models.
Start with a straight-across measurement
Width or diameter describes a distance across a part. Girth measures around it. Look for the widest insertable dimension and ask which part the listing measures if it just says width.
Separate the base and body
Overall length can include the neck or external handle. Use insertable length when comparing usable dimensions and check the base separately.
Treat size words as labels
Small and beginner describe a retailer’s category. They do not guarantee fit. For comparisons of sets rather than individual models, see the graduated set measurements guide.