Stackmat (officially stylized StackMat) is the official timer of Speedstacks and the standard timer used in WCA competitions. There are two brands of stackmats, the QJ and the Speedstacks, but only the Speedstacks one is used at competition. At least the Generation 2 timer must be used. QJ timers are much cheaper than Speedstacks timers, and one of ttheir timers (3rd gen) has a data port, although none of the QJ models have a data storage feature. QJ has 3 models, but the 1st gen timer is not produced anymore.
Pre-WCA use and official adoption
Gen-1 (Generation 1) Stackmat timers were first used in World Championship 2003 [who decided this?] and since in every official competition. Tyson Mao used them in the first Caltech competitions in early 2004. When the World Cube Association was founded later in 2004, Stackmat timers were adopted as the official timer. The major rival was a timer developed by the official Rubik's brand around 2003. This timer used a light sensor, which is stopped by when the solved cube is placed on top. Among the reasons for the adoption of Stackmat was the real possibility of accidentally dropping the cube, especially during a one-handed solve. Stackmats, which required two hands to stop and so signal the solvers' intention that the solve is complete, was deemed a better solution.
- In the large tournament display, the times are shown delayed. As a result, after stopping the timer, the display often seems to "jump" as much as 0.3 second. In most cases, the timer itself times accurate timing. However, there are known cases of verified mistiming, such as this Master Magic solve by Bob Burton in 2005.
Accuracy (timer frequency distribution) issue
Gen-2 Stackmat timers, or at least earlier versions of them, do not show all times uniformly; see for example the following links:
- This chart of distributions (Stackmat vs. QJ)
- Thread about the distribution
- Thread by Tyson Mao about the next generation of Stackmats
- Post about distributions by Stefan Pochmann
- The top-ranked magic results
- The large tournament displays cost $100 each and are connected by small cables that can easily break or go missing, rendering the whole display unusable.
- Gen-2 timers have the reset button between the hand plates. When stopping the timer, the solver may accidentally hit reset with the thumb, making the time DNF. Although this was seen as a major problem at the release of Gen-2 timers, especially for blindfold solvers, there have since been no high-profile (e.g. world record nullified) case of this issue. This was one of the reasons some cubers saw the Gen-2 timer as a step backwards from Gen-1.
Gen-3 Stackmat timers
Gen-3 Stackmat timers were announced in 2011. They time to thousandths of a second. The WCA decided truncate the results; results will be recorded on the scorecards to thousandths, but only hundredths will be entered into the database. Although this solves the time distribution problem of Gen-2 timers, Gen-3 timers introduced some new issues, most notably some timers failing to stop or resetting when stopped. As of US Nationals 2012, Speedstacks is no longer producing Gen-2 timers.
Place to buy
- Speedstacks official Shop 
An iPhone port called TapStack© provided by ©ompactGames.