It is packaged using the Tape & Reel (TR) method since it is a clock IC. RF synthesizer is comprised of CLOCK GENERATOR, PROCESSOR SPECIFIC uPs, uCs, and peripheral ICs.
SI5351A-B05518-GTR Features
SI5351A-B05518-GTR Applications
There are a lot of Silicon Labs SI5351A-B05518-GTR Clock Generators applications.