I had a problem with the little plastic anchor these strings were attached to breaking. Here is a site where these anchors and other shade parts are available. They also have videos of how to restring blinds when the time comes as well as parts needed. If you don't know for sure which string you have they will send 3 free samples for you to do a look see. I have ordered from them and their service was excellent.
2006 GMC 2500HD CCSB 4x4 Duramax/Allison, Titan 52 gallon fuel tank, Prodigy Controller, B&W Companion Hitch
2010 Jayco Designer 35RLTS, Cummins/Onan RV QG 5500 EVAP, Progressive Industries EMS-PT50C, TST Systems 507 TPMS, RV Flex Armor Roof