There are several (or was). They are the normal standard size(s) and can hold a considerable amount of food. The food that is stored is expected in relatively small soft sided containers and NOT like the ice chest I saw one tourist trying to stuff in there by pulling all the other's packages out first. I sort of ambled over and asked what she was going to do with all the stuff she pulled out.
There is a campground there, so you have a relatively large population that would like to participate in starving the poor bears.
There is a large hiker/backpacker parking lot that is often overflowing with back packers putting their stuff in there temporarily to head out in the morning. There are back packers who leave food in there for several days because their pack turned out to be bigger at the trail head than it was at home. There are some who leave food there for long haul back packers who come out for resupply. There are some that, with all the best intentions, leave their extra food behind to share with others. And there are a rare few trail bums that live off the contents of bear boxes.
The contents of all bear boxes are at the whims of whomever is there before you. The earlier you get there the better chance of finding space.
Pack your food in brightly colored bags that you can identify as YOURS easily with a flashlight. Make sure you get ALL of your bags when you leave.
What can go in there is what can't fit in your personal bear canister.
Of course, consider the next 20 or so people coming in behind you.
What you might consider as a last ditch effort, is sleeping with your food in your car. If you get hustled in the middle of the night, make sure the key is in the ignition so you can make a quick get away to outpace the critter(s) on the way down the hill.
But you gotta be quick! They are.
