About Us

Where Precision Meets Passion

We take pride in combining professional craftsmanship with a personalized approach, ensuring every player — from juniors to seasoned competitors — gets equipment that truly fits their game!

Our team brings years of tour-level experience to each service, from custom stringing to frame tuning and player consultation.

Meet Our Team

At Tennis Lab FX, we’re a small team with a big passion for the details that make great tennis possible. From tour-level stringing to frame customization, we’ve spent years perfecting our craft and love sharing that expertise with every player.

Our goal is simple: to help you feel completely connected to your game. Whether you’re testing new racquets or fine-tuning your setup, we make sure your gear performs exactly the way it should.

Tim Keller - Owner

Yat Kong - Head String Educator

Yat has been stringing racquets at the highest level for over 40 years, working with players at all four Grand Slams and some of the biggest names in tennis: from Nadal and Sampras to McEnroe and Navratilova. His experience spans decades of innovation in custom stringing, racquet tuning, and frame care.

Here at Tennis Lab FX, Yat leads our team training and stringing education. He’s the one making sure every frame is handled with tour-level precision — and that the next generation of stringers carries that same passion for detail and feel.

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. Her work ensures every frame performs with the consistency and control players need under pressure.

At Tennis Lab FX, Ana leads by example, combining deep technical knowledge with a calm, meticulous approach. Her reputation for accuracy, reliability, and quality craftsmanship sets the tone for our stringing team and reflects the tour-level standards we deliver every day. Fluent in English and Spanish, Ana connects effortlessly with players from around the world who trust her attention to detail and expertise.

Ana García -

Len Filatov is an experienced professional tennis stringer and a proud member of the Wilson International Team since 2006. With nearly two decades of expertise, he has provided world-class stringing services at the sport’s most prestigious events, including the Australian Open, Roland Garros, Wimbledon, and more than 20 consecutive US Opens.

Len has worked at major ATP and WTA tournaments worldwide, serving both as an official and private stringer for top-ranked players. Since 2017, he has been part of the official stringing team at the Laver Cup, contributing to one of tennis’s most elite competitions.

His professional journey began at RPNY Tennis in 2005, where he refined his craft and developed the precision, consistency, and professionalism that define his work today. Known for his meticulous attention to detail and commitment to excellence, Len Filatov remains a trusted expert among players and professionals across the global tennis community.

Len -

From local tournaments to major international events, our team has supported players and stringing crews at every level — always with the same care and precision.

With years of tour-level experience, we combine professional craftsmanship with a personal touch, making sure every player gets equipment that truly fits their game.

Past Events Highlights

Miami open 2014 with Roger Federer and the Wilson team.

Tim Keller, Owner of Tennis Lab FX. 2024.