Features:
Height overall including drain fitting - 4"
Height overall excluding drain fitting - 3-1/4"
Diameter overall lip outside - 4-1/4"
Diameter inside (large) - 3-5/8"
Diameter inside (small) - 2-5/8"
Hole cutout needed - 3-3/4"

Small Tips from Valued Customer:
If you're creating a “standard hole size” you're looking for a 3 and 5/8” hole saw.
If you're going to be drilling into fiberglass, here's a few tips:
1. Put painters tape down over the are you'll be cutting out. It'll help keep the drill bit from wandering all over the place and scratching up that gelcoat you work so hard to keep clean.
2. If you're using a standard hole saw bit for your drill, it'll have the standard drill bit in the middle along with the big honking hole saw bit on the outside. Once you drill through the gelcoat with the center (smaller) drill bit, put the drill in reverse and let the drill back its way through the first layer of fiberglass before switching it back into forward to remove all the bulk of it. Running it in reverse first will lesson the chances of it cracking and spidering out everywhere. It's typically a much cleaner cut.
3. Run the drill in low speed. You're removing a bunch of material so don't go heavy on it. You're likely to overhead the bit and the saw will lose its temper (both literally and figuratively).

Customer Service:
If you have any question or suggestion about our product, please feel free to contact us. Your 100% satisfaction is our pleasure.
Whenever you install any product, please follow the installation manual and take care of the protective measures.
If you like our products and services check out our store for different sizes and models ladders.