Excerpt from a story I just read on the internet

The third finger soon slipped in. He shuddered, his body stiffened, he groaned, but made of sign of wanting me to stop. The in and out rolling movement continued, he relaxed, took it, and began to enjoy it. 

With no notice, I added the fourth finger. He seemed to be primed to take it. His groaning was turning into a deep gutteral growl. I sped up the in out rhythm, I was also practically spinning my hand. Now I decided it was time to go the whole way. I added my thumb to the rest of my fingers and shoved as hard as I could. My hand met with a lot of resistance at the wide knuckles. I pulled the fingers out and jammed them in again, again the stopping. His body stiffened, I worked the five fingers around until he relaxed again. He opened his inhaler, and took two deep draws from it. I could feel the heat surge into his ass. I pushed again, and this time my whole hand entered the hole. 

There was that terrific feeling, of damp, moist, warmth. Inside of his asshole was like velvet. He really growled when my hand slipped in, but I never stopped the rotating movement, I just slowed it down, so he could get the feeling of the entire hand moving around inside of his guts. I had to admire him, there aren't a lot of nineteen year old, 145 pound boys who are able to take a big man's fist into their ass, and especally not on the first attempt. 

I now had my courage up and started to work my arm into him, a little at first, increasing it as I fucked him. Soon it was no problem at all to be sinking my arm into his ass almost up to my elbow. The feeling for me was great. I loved the feel of the warmth and tightness. It felt like a long velvet glove on my arm. He was making funny little sounds, and his head was rolling in sheer ecstasy. I fucked my arm faster, and rolled my hand inside of his gut, he cried, not from pain or discomfort, but from joy and pleasure. He had a big smile on his face, he was now making gurgling noises and tears were flowing out of his eyes. "More, more," he whispered, as he tried to push his body against the impaling arm. I pulled my arm out of his ass in one quick move, there was a popping sound as it came out. 

"NO!" he screamed, "Don't, Don't take it out, Please, ram it back in, Quick, please, I need it, please." Again, with one stroke, I drove my fingers, fist, and then arm, right in up to the elbow. I could feel his guts spasm around my buried arm as he screamed, "I love it... love it... love you... more... more." I decided to do it good, so again, I pulled my whole arm all the way out. This time, however, as soon as my fingers were out, I jammed the whole thing back in again. One long smooth stroke from fingertips to elbow.