About
About the Lab
A racquet studio built for New York players who take their game seriously, and those who are just getting started.
A studio, not just a shop
Tennis Lab FX was built on a simple idea: New York players deserve a place where they can get honest answers, expert stringing, racquet customization, and real gear recommendations, without the hard sell or the guesswork. Our stringing team brings decades of tour experience, including all four Grand Slams, to every frame that comes through the door.
We're not a big-box store. We're not an online retailer. We're an all-in-one studio tucked into Midtown Manhattan on East 51st Street, open Monday through Friday.
Everything here begins with a conversation. We ask about your game, your arm, your tension preferences, and your budget. Then we get to work: stringing, customizing, and building setups on professional equipment, with real attention to every detail.
We believe the right setup can genuinely change how you play. We take that seriously, without taking ourselves too seriously.
The Lab philosophy
Six principles that guide how we work, what we stock, and how we talk to every player who walks through the door.
Precision Over Speed
A rushed restring is a bad restring. We take the time to do it right, every time, for every player, regardless of level.
Honest Advice Always
We don't upsell. If the expensive string isn't right for your game, we'll tell you. Trust is built on honesty, not enthusiasm.
Built for New York
NYC players are time-pressed, informed, and serious about their game. We're here specifically for them and the city they play in.
Ongoing Education
String technology evolves. We stay current so our recommendations are always grounded in real knowledge, not just habit.
Every Level Welcome
From weekend warriors to competitive players. No question is too basic. The lab is for anyone who wants to play better.
Every Setup Is Personal
No two players are the same, and no two racquets should be treated the same. We build setups around the individual, and document them so the work holds up over time.
The people behind the bench
Every racquet that comes through Tennis Lab FX is handled by someone who plays, studies the craft, and genuinely cares about the outcome.
Tim Keller
Tim is a career tennis professional with experience in high performance coaching, player development, and advanced movement systems. Certified, insured, and immersed in development for every level in the game since age 20, he operates between tennis performance, biomechanics, and equipment optimization.
A specialist in tennis biomechanics and kinetic chain efficiency, Tim has built a reputation for translating complex movement science into practical, on-court performance. His work extends beyond stroke mechanics into how the body interacts with the racquet, strings, and load over time. This is now a core principle at Tennis Lab FX.
His background spans elite tennis environments, including work with the USTA, New York Junior Tennis League, Arthur Ashe Foundation, and high performance roles at private member clubs and organized programs such as Courtsense Tennis Academy. He has also trained with and supported ATP and WTA professionals, giving him direct exposure to the demands of the highest level of the sport.
As a player, Tim competed at the NCAA Division I level, with experience in national and international tournaments and ITF events, bringing firsthand understanding of competitive tennis and its physical demands.
What separates his approach is depth. His studies extend into sports psychology, physics, strength training, movement disciplines, and performance nutrition, allowing him to build complete tennis performance systems, not just coaching sessions.
At Tennis Lab FX, this translates into a precision-first philosophy: every racquet setup, string choice, and customization decision is treated as part of the athlete's performance system, not an afterthought. For pros and beginners alike.
Tim's work is driven by one principle: maximize potential through precision, regardless of level, age, or starting point.
Jon Feigelson
Jonathan has been a New Yorker his entire life, and a tennis player for most of it. Thirty-five years on the court will do that to a person. It stops being a hobby and starts being part of who you are.
His connection to the sport deepened through a friendship that spans more than three decades with Roman Prokes, whose RPNY community became a touchstone for serious players across the city. When that chapter closed, Jonathan felt the weight of what had been lost and the pull of what could still exist. Rather than let that spirit fade, he decided to carry it forward.
Tennis Lab FX was born from that conviction. Alongside his friend and coach Tim, Jonathan set out to build something that honored the legacy of RPNY while creating a home of its own. A place where craft, care, and love for the game live under one roof in Midtown Manhattan.
Ana García
Has talked more players out of bad racquet purchases than she's completed. Knows the full string inventory by hand feel and can fit a grip in under two minutes. The person to ask if you want a straight answer on whether a piece of gear is actually worth it.
With nearly two decades of experience on the professional circuit, Ana has become known for her precision in racquet stringing and customization. She's worked at some of the world's top tournaments, including the US Open, Australian Open, Miami Open, and Indian Wells, supporting elite athletes who rely on flawless racquet preparation.
At Tennis Lab FX, Ana leads by example, combining deep technical knowledge with a calm, meticulous approach. Fluent in English and Spanish, Ana connects effortlessly with players from around the world.
Len Filatov
Thousands of installs deep. Knows poly from gut by feel. Always happy to talk tension for ten minutes longer than you expected.
Len Filatov is an experienced professional tennis stringer with an impressive background in the sport. He is a certified stringer and has honed his skills through years of dedicated practice and hands-on experience. Len has had the privilege of stringing for prestigious events, including the US Open, where he contributed his expertise to support professional players at the highest level of competition.
In addition to his stringing work at major tournaments, Len has strung for several high-profile players, gaining a deep understanding of the unique preferences and requirements of elite athletes.
Yat Kong
Strung racquets at the highest level for over 40 years. Four Grand Slams, the biggest names in tennis, and four decades of expertise in custom stringing, racquet tuning, and frame care.
Yat has strung racquets at the highest level for over 40 years. He has worked with players at all four Grand Slams and some of the biggest names in tennis, including Rafael Nadal, Pete Sampras, John McEnroe, and Martina Navratilova. His experience covers decades of innovation in custom stringing, racquet tuning, and frame care.
At Tennis Lab FX, Yat leads team training and stringing education. He ensures every frame is handled with tour-level precision and trains the next generation of stringers to match that same focus on detail and feel.
Johnny Luis
Johnny came to tennis the way a lot of New Yorkers do, through watching, not playing. A longtime fan of the game who grew up following Rafael Nadal, he developed an appreciation for the craft and intensity that defines the sport at its highest level.
These days, he's on the court a little more himself, still learning, and genuinely curious about the world he's now part of professionally.
At Tennis Lab FX, Johnny leads the digital side of the operation, building and maintaining the website, developing the tools that help customers find the right gear, and supporting the team's marketing efforts.
Come visit the Lab
Walk-ins always welcome. 235 East 51st Street, open Monday to Friday, 8:30 AM to 6:00 PM.
Get Directions & Contact