Typically, if it isn't hurting when you playing around in your butt, that means nothing is getting torn or significantly damaged. That being said, it is safe to insert things deep into the rectum and even around the bend to the sigmoid colon. This is what is done during a colonoscopy; a camera is guided all the way through your colon. I would not suggest using LONG toys that are also rigid and wide in nature. Approximately 8 inches into the rectum, you reach a bending of the bowels. This is the start of the sigmoid colon. If a rigid and wide toy were to be inserted that far into the rectum, it would press up against the wall of the bowels and cause extreme discomfort because it would be unable to conform to the loop in the colon. The anal beads that you linked to should be safe for this kind of insertion because they are very flexible in nature and only 1" in diameter. Some bowel movements are MUCH larger than this LOL. Just be careful and only use flexible toys to explore that deeply in the rectum. I hope this helps!