Instruction: Answer the given question by extracting information from the supporting document.

Input:
Question: What is the approximate diameter of the widest part of the mixing attachment? Need to know if it will fit into a baby bottle.
Document: I ordered this item to mix thickening liquid for a nursing home, and found that it is only good for thin liquids such as milk or water. The problem is the attachment staying connected in the housing part, and not falling out during the mixing process of about 4 ounces. After a few tries, the little stir attachment no longer stays attached when inserted, and keeps falling out rendering the Mixer useless.
The pieces are to short to reach the bottom of a regular glass. To power the mixer you push a plastic part down. The plastic did not fit in the slot for battery power. Useless. Spend the money on a better product.
I used one of these years ago and it took a while to figure out what search terms to use. It's fine for what it is but I'd pay a dollar more for better construction. The straight attachment wobbles and takes a 2nd hand to get it going. Not practical for mixing with the one. The others are similarly cheap in construction. The metal one works great. I don't know if it's worth the bother to request a repalcemnt.
If you don't know what Bulletproof Coffee is and you regularly drink coffee, you really ought to Google it. Basically it's toxin/mold free coffee with coconut oil extract (MCT oil) and grass-fed butter (Kerrygold). Absolutely delicious. Makes the brain go yipeee with no crash. This mixes everything up and leaves a nice froth on top. I use the pencil shaped attachment that spreads apart while mixing.
I've owned several of these little mini mixers. I wish that they were all better, more powerful, built stronger. This is just plastic with a tiny motor running on 2 AA batteries. But, I use it for mixing baby bottles, protein shakes, individual juice packets, hot cocoa, and for that it does pretty good. I go 2 months between battery changes with daily use. I only use the little metal attachment, as I don't feel it has enough power to made the whisk worth using.
This little mixer has amazing power and many uses. I love it for mixing jello (use the little metal attachment) my husband loves it for mixing powdered drinks into the water. Great for hollandaise sauce, frothing drinks, hot chocolate or anything you need to mix in small amounts. After I got mine, I showed it to friends and family members who all want one now. I plan on buying several for stocking stuffers this Christmas.
These little mixers fit where the others can not go. I use the slim wand reaching down into the neck of a water bottle to whip up the tea mix I pour in. Great little mixer. Highly recommended. I bought three and gave two away to friends.
The batteries were really hard to put in as there were no - or+ signs to follow. Also, when I put the mixer part in, it stayed in. The attachment & a part of the end that holds it comes off together, therefore, I can't use the other attachments. The mixer works well, however. Lee Ford, Scottsdale, AZ
The Fit & Fresh model, that looks the same but has only the plastic whip (prong) attachment is a much better-made motor housing. I've bought three of these for use in various places (home, office and camper). The Norpro has an incredibly cheap depression switch that barely manages to make contact with the battery, if at all. I've tried to reassemble it, but that did not work.
I had one of these several years ago under a "Betty Crocker" label. It only had one attachment. When it finally wore out I could not find one to purchase again. I finally found this on Amazon. It has lots of power for its size and intended use. Works great. My only problem is that the attachments fit very tight. It feels like I'm going to break the mixer with the force required to remove the attachment. But so far so good.
Answer: As the picture shows, there are four attachments.  The narrowest is 3/16 of an inch wide.  The widest is 13/16 of an inch wide.  The other two are 11/16 and 3/4 of an inch wide.  They would fit in the baby bottles I have seen.