Product review (4 stars): one / year is a recommended by Rinnai and other manufacturers
Purchased these hoses to use with a tankless water heater flush kit I am assembling: Two 8' foot washing machine hoses and 1/6-hp utility pump,(both from Amazon) plus 5-gal bucket w/ lid from local box-store and RectorSeal flush.kit from local plumbing supply house. Have not yet used because just had plumber flush ($200) while doing other plumbing work. Building your own kit is much less costly than buying the kit unit on Amazon. Got the SS-braided hoses for longevity sake and expect them to hold up well. Anyone with a tankless water heater needs to know that flushing ca. one / year is a recommended by Rinnai and other manufacturers. Online YouTube suggests using three generic one-gallon containers of distilled white vinegar does which should perform just as well as the commercial flush. With this hoses and self-assembled kit (ca. $75 total vs. $135 Amazon's pre-assembled kit), I will save myself hundreds of dollars each year by doing flush myself, a rather simple 1 to 1-1/2 hour process. Be sure to get these SS-braided hoses to go in your kit  or to change washing machine hoses every 5 years as recommended.