This is a awesome product! I was able to finish my laser machine . Some people say that the blocks are too loose, some are but they have adjustable screws to make them the right tension.
48 inches, straight, no binding. Bearing blocks have smooth motion. Glad i bought 3 sets. No trouble with any of them. 4 stars because i have never rated anything 5 out of 5. These are beefy and worth the price to me.