The 'normal' one.

"I bet you are looking to get it on with that one there," she points to the one with the head you couldn't wrap your arms around. You go wide-eyed as it raises up from the hanging mass as it hardens. It is as thick as the widest part of her thighs. She traces her fingers along the length lovingly. "Why am I the only one with my cocks hanging out?" You disrobe slowly. "Yeah, I like a striptease," Becca says lustily. You were just taking your clothes off slowly because of your apprehension. She cheers when you are totally naked. She slips out of her top too so her titties wobble freely with her movements. "We aren't really going to start with that, you know? That will take work! We will start with the normal training one first." That one rises to hardness and the other softens. "Bend over and spread em!" You bend over and spread your butt for her. You soon feel a luckily slimy hard object running through your crevase. She pushes at your hole when she gets there. She doesn't waste time! The end is very narrow and glides in easily. The end seems flexible once inside and you feel her other cocks around you as she snakes through you until she easily bottoms out. "Someone has done this before," she snickers. "Your toys must be larger than this, unless you take cock?"
"No, no cock until now," you grimace.
"Good, let's shove a second in here then. The normal one." She pulls out until you feel the end leave you. Then you feel two distinct cockheads enter your ass. This is more of a review for you than a lesson in assplay. "Oh, making this look easy, are you? This should prove more your speed!" She pulls out, and then you feel the fatheaded normal width cock pushing at your hole. The wet thing gains entry easily once you relax for it. The previous two slide in after that one.