I assumed these were all the same type of product, usable on both hardwood and carpet floor. There are actually 2 types, half for carpet and half for hardwood. I used the hard sided ones (for carpet?) under my dryer and extremely heavy washer, on our garage which is concrete covered in epoxy. They work great for this purpose! I couldn't even move the washer 1 inch before. Not sure how the felt ones will work. 1 star taken away only for the lack of clarity regarding the product.
2 different sliders; very useful