The dropper half
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What is available
60 glass Boston rounds, 49 PET Boston rounds and 32 PET imperial bullet cosmos in the small window, with 43 dropper assemblies, 6 dropper tips and caps and 16 flip tops behind them.
The bulb dropper
Measures by eye against the graduations, which is fine for a careful dose and slow when an animal is moving. It also leaves the bulb in contact with the product between uses.
The flip top
Delivers a line rather than drops, one-handed, with the cap closing against a thumb. For a spot-on applied along a back that is the better mechanism.
Glass where the formula is aggressive
74 glass containers. A topical carrying essential oils or solvents attacks plastic and adhesive, and glass removes the bottle from the argument, leaving the bulb, the liner and the label.
Amber where light matters
69 amber containers. For an active that degrades in UV this is the cheapest protection available, and it costs nothing in usability.
20-410 and 24-410 are the finishes
107 and 84 respectively across the shelf. Both are well populated with droppers and flip tops, so a container on either keeps the applicator decision open.
Test it the way it will be used
Outdoors, in gloves, one-handed, on an animal that moves. A dropper that works beautifully on a bench fails that test regularly, and the failure is the product rather than the packaging.
The bulb is a material question too
It sits in the product between uses, so a formula that attacks rubber or the dropper tip degrades the applicator rather than the bottle. For an essential-oil-heavy topical the bulb is the first thing to test.
Graduations are worth paying for
A dose measured against printed marks is repeatable; one measured by counting drops is not, because drop size varies with viscosity and temperature. For a dosed animal product that difference is the product working or not.