Fill Nipple Covers (what is your preference)

"Tominco"The Ninja is the same as the AoA style. 
Another, super cheap, option is to go to the hardware store and find a rubber screw thread protector. Here's a link of something like what I'm talking about (But, I'm not sure on what size you'd need). 
I have the AoA (Ninja) style and a rubber cap and I still use both. 
Tom


Tom, I'm so glad you posted this. I used that plastic screw protector you just mentioned and I have one of the rubber nipple covers crammed down inside it. Worked perfect on my Disco after I put the TKO on the end of the barrel and the regular fill cover would no longer fit due to close tolerences.
The plastic nipple holds the inner rubber nipple tight enough to remove and replace for very fill with no problems so far. But I still want to check out the magnetic and ball bearing fill covers just for $hits and giggles ;-)








 
Campfussell - I had to resort to something when I added the Atlas rail to my Verminator. The threaded inserts protruded too far into the stock and my OEM cover wouldn't fit anymore. Kind of like you and your Disco. Those make a good cheap fix that you don't get too upset over if you misplace. I have recently fixed the insert and my OEM cover fits again. :)
These are called plastic but, the ones I'm using are not a hard plastic. They're more like a soft rubber material. They're used a lot where screws protrude and could end up cutting someone. Like underneath a picnic table. all they do is cover the threads so, people don't get sliced if they bump into them on accident. 
Tom