Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: What is the diameter of black plastic on the 3.5mm? Basically, will the 3.5mm end fit into my iPhone with my case on?
Document: Does what it is supposed to do but the housing at the mini plug end is a little too big to fit through my iPhone's Otter box case, which means I have to take the iPhone out of the case in order to connect the iPhone to my stereo receiver.
Basic cable here, nothing special. The only complaint that I would have is that the 3.5mm connection does not connect to my phone with the case on, the plastic part is too wide. But that is not the fault of the cable. 5 stars because the price is right and it works with no issues.
I love that I can just plug my phone into the little cable that I have hanging out and ready for it, and music comes flooding out from real speakers the way it was meant to be heard.Cable works well, no noticeable signal noise, and the 12 foot length makes it easy to position the 3.5mm end wherever you want it (I leave it next to my iPhone charger).
This cord is one month old today, and the 3.5mm end is fraying already. I am guessing the cord will fail to work in the next week or so.I should have done it right and payed more for a better quality cord the first time, instead of buying a cheap one first.
90% of the time it will not work and you have to wiggle and bend the connection at the 3.5mm end to find a spot where it will work. FWIW I have been using this on a daily basis and plug and unplug it multiple times so for the price and a years worth of abuse I would still recommend it. But now I am looking to purchase a replacement.
It plays sound through it from my iPhone which is why I got it, but I have to take the case off. Since it isn't made for it I guess I don't really have a complaint, but it would be nice if the adapter was a little more thin.
Basically it is what the description states. A 12 Foot RCA to 3.5mm stereo cable. I have purchased several of this type of cable over the years for transmitting audio from laptops and MP3 players to a stereo.I have payed over 10 dollars previously, I decide to give this cheaper product a try and I must admit I was expecting them to fall apart without actually touching them.The cable quality is on par with cables I've purchased from B&Ms.
Extremely low quality, broke within one week of normal use. RA end has loose fit and requires some wiggling to get proper sound
This cable fit perfectly. It is connected to the rear RCA jacks in our 2004 Honda Odyssey with RES and runs hidden along the floor/carpet to the pullout cupholders just below the factory radio head. This allows us to connect various devices (ipod, iphone etc...) to the factory stereo with good sound. For a mere three dollars, who could argue such an inexpensive upgrade considering the costs with other methods of connecting such devices to 9 year old tech. Very, very nice!
I bought this item hoping that it would disprove my doubts - it did NOT. As is usually he case, you get what you pay for. Do not buy these cables if you want quality cables. These ones produce tons of static when connected. I am now looking to buy the same cables but this time I'll pay more than $3 for them.
Answer: It seems you have some contradictory answers,  probably because nobody (but you) knows what case you're using and how large a hole is available at the audio port.  Here are the actual measurements so you can measure your case and decide for yourself.   The plastic actually tapers a bit.   It's 10 mm in diameter at the pin end,  11mm at the cable end.   The black portion is 23mm long.  The audio pin is pretty standard at 14mm.