I created caps to allow for comfortable on-the-knee dumbbell exercises with adjustable dumbbells. Using these will prevent you from experiencing pain from the shaft. This listing is for a set of 2 caps. (Dumbbells are not included.) We have sold over 180 sets to date. If the product breaks within 2 weeks of use, provided you follow the usage precautions, we will replace it free of charge. The size is slightly smaller than a 1.25kg plate to prevent breakage. I use IROTEC screw-type dumbbells, but I believe they can be used with 28mm screw-type dumbbells. I was able to use 3-4 plates including the collars. *The screw part needs to be exposed by about 1.5cm for attachment. Each cap weighs approximately 70g. The material used is durable ABS. I have been using them for about half a year since creation without any breakage. (With weights around 25kg, used every other day) Please understand that these are handmade items and may have small burrs, dents, or scratches. ☆Usage Precautions ・Although the photo shows the dumbbell standing upright, please refrain from doing so as it may cause injury or breakage. ・Do not overtighten the caps more than necessary, as this can cause breakage. ・Do not drop the dumbbells, as this can lead to breakage. ・Do not use the caps themselves as collars, as this is dangerous. ・Avoid direct sunlight, as it will accelerate material degradation. *This item is not eligible for discounts. *Please note that I only sell on Mercari and not on any other platform.