After this period of profound training with some of the most inspiring “teachers” and companies, he began to define the style that characterizes his personality and his idea of design. Marco Romanelli, curator and editor of Abitare Magazine, summed up some characteristics when stating: “Klaus´ design resembles Klaus (do not be amazed: once upon a time there was fervent belief in a correspondence between the creator and his work): strong, decisive, without trimmings. It comes from the simplicity of country and alpine life, from the veneration of anonymous design, from the observation of daily behaviour. ...”

Consequently, in winter 1998/99, he set up his own office in Munich. The time in Morrison´s studio led to an ongoing involvement in a couple of architectural projects in Germany for companies like Stroer and Vitra. Furthermore, Hackl´s office began to work with a constantly increasing number of regional and international manufacturers. Striving not to accept only a specialist view of design but to work with a wide range of challanges instead, the list of clients has expanded and today includes companies as diverse as Magis spa, Nils Holger Moormann, ENO - edition nouveaux objets, Side by Side, Pinakothek der Moderne / Palais Pinakothek, Lifebridge AG amongst others.
For the Italian company Magis he created the plastic laundry bin «Gibus» (2001), a truly useful, mass produced everyday household item. He also became one of the main designers who contributed some notable products to the collection of Side by Side, a socially responsible company that has their handmade products manufactured in a network of workshops for handicapped people.
His 2003/2004 solo exhibition in Saarbruecken was accompanied by a monography «Klaus Hackl - Zwischen den Dingen» giving a complete overview of his work to date and revealing the impetus, values and philosophy behind his designs through texts by Florian Aicher, Andreas Brandolini and Jasper Morrison.
Following the invitation to design a wooden chair for Promosedia (2005), he was asked to participate in a group show together with Front, Polka, André Klauser and Kram/Weisshaar at Rossana Orlandi Gallery in Milan one year later and on the occasion of the Milan Furniture Fair in 2006. This exhibition led to him beeing invited to design some household products for the brand-new collection of the Paris-based company ENO teaming up with collegues like Arik Levy, Sebastian Bergne, Gijs Bakker and Paola Navone.
His laser cut aluminium light «Pelle» (1998) was selected for the International Design Yearbook 1999/2000. Later his lamp «Wenig» (2005) was chosen for the “Super Normal” exhibitions in Tokyo (2006), London (2006), Milan (2007) and New York (2008). Recently, Klaus Hackl´s work was also part of the prestigious exhibition “design germany: case study 2008” a show highlighting “... a selection of classical and current German designs ...” held first at the “imm Cologne” in January 2008 and again on the occasion of the reopening of “Die Neue Sammlung” at the Neue Museum Nuernberg later the same year.
More recently, together with Uli Guth, he finished the progressive design work for the first portable heart-lung machine worldwide, the «Lifebridge B2T®». Striving to design an adequate visible expression for a completely new medical device typology it took more than five years to downsize and organize all internal components without loosing functionality.
The design was awarded an IF and reddot prize (2008). As a result of this successful collaboration he teamed up with Uli Guth to form a joint venture (Arge Guth & Hackl) trying to tackle some new and demanding challenges in the complex field of medical design.

At the same time Hackl´s office is also known for its interest in less commercial activities. Apart from designing and curating exhibitions, he is trying to improve the exchange of ideas between craft culture and design by establishing networks and collaborations with contemporary craftspeople and craft institutions like Werkraum Bregenzerwald, Handwerken and the Bayerische Kunstgewerbe-Verein. Well aware of the fact that an important part of design history is rooted in craft, his research aims at evaluating, updating and learning from those qualities of work ethics, highly skilled manual production and regional distribution which have been familiar to small local workshops for centuries.

His career has also included teaching design at the Saarbrücken School of Art and Design (2002-2003). More recently, he was invited to give lectures and hold workshops at design schools in Germany and abroad. He was asked to participate in design talks:
at the Promosedia fair (2005), the Institut für Wirtschaftsgestaltung (2006) and at the design office Designafairs (2008) just to mention a few.