Very tight fit...had to use pliers to get it to go in all of the way. Size and finish is perfect though. I purchased a 8 gauge replacement ball for an 8 gauge circular barbell that I have had for years that was originally purchased at a Razz-Matazz, a t-shirt/novelty gift store in my local mall here in IN. I am very happy with the purchase because I was having major problems with my balls falling out and having to look for them. I would rather have them never fall out than fall out all the time. Would purchase again!