Amazon.com : Hycline Shimano Bike Rear Derailleur RD-TY21B 6/7 Speed Direct Mount for Mountain Bicycle-Black : Sports & Outdoors
New 7 speed commuter with Shimano SIS index. No noise on stand, shifts smoothly but low clanking sound on road when pedaling in 4th & 5th though not other gears : r/bikewrench