1. Built-in bubble level helps make horizontal adjustments easyn2. The center column can be inverted for unusual low angle shotsn3. For speed and convenience, each leg has an automatic leg angle lock mechanismn4. 2 position leg angle for uneven terrainn5. Your choice of economical aluminum or light weight carbon fibern6. R2/R3/R4 Series has retractable spiked feet for outdoor photographynnThe SIRUI R series tripod line is broken into two different categories - the conventional R1 and R2 series tripods offer many desirable features including:nnA Center Column locking collar with a special design that is very convenient to use - even while wearing gloves in cold weather.nnA tripod mounting plate with a double headed, reversible screw that accommodates 1/4" and 3/8" tripod sockets.nnA useful built-in bubble level to help properly align the tripod.