Mountain bike groupsets: everything you need to know - BikeRadar
Amazon.com : Rear Derailleur, Huazu Bike Parts Gear Shifter for Shimano RD-TZ31-A with Direct Mount/Hanger Mount for 6/7 Speed Mountain Bicycles : Sports & Outdoors
Shimano Deore RD-M5130 Rear Derailleur - 10-Speed, Medium Cage, Black – Bicycle Outfitters Indy