Most rollers don't have the same bolt sizes, or even the same mounting systems. Unfortunately you're seeing why plastic in rollers isn't a good idea. I've even seen the plastic endcaps on Kreitlers go bad.
Rollers are one area where you pretty much get what you pay for. Every extra bit you put into a pair of rollers will reward you with a better ride, and there's a reason why Kreitlers have been on top for so long. These days the one real contender is the TruTrainer Traveler (www.trutrainer.com
). It's identical to the TruTrainer Premium but without the flywheel. It's the same price as a Kreitler, same money-back guarantee, but made much better and with higher quality materials. Kreitlers are overpriced for what they are; TruTrainers make up the quality difference and are worth the price. They're a good piece of change, but if you can do it, they make the difference between having rollers that sit in a closet year-round and rollers that you actually ride.