Customer Rating: - Not Designed Correctly
Although Bosch claims this extension works with the 4100, it has a problem. Both screws from the left bracket(the one with the longer rod) cannot be screwed in because the curve of the body of the saw blocks it. So you either use one screw which causes the left side to bend with any eight, or you need to machine a hole yourself.

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Customer Rating: - Update - Great Bosch Service - was: Does Not Fit 4100 Series Saws - Beware
I am editing this review to report that Bosch provided great service on this issue. I spoke with customer service and ultimately with the product manager today and they're sending me a replacement part that should solve the problem. Problems happen - but Bosch was very responsive on this issue. Thanks, Bosch. (I am leaving the original review below so that others who experience this problem will hear that Bosch will resolve the issue.)

I purchased this for my (excellent/5-stars) Bosch 4100-09 saw. The box and the instructions specifically state that it will fit this saw, as well as the 4000-series saws.

Well, there is no physical way to attach one of the support brackets at all - there is significant physical interference from the saw housing that prevents bolting one support on. Further, it appears that even if both supports could be secured to the underside of the table, the front rod will physically interfere with the table extension lock lever.

I cannot imagine how Bosch could get a product this badly wrong onto the market. If you own a 4100 saw, beware.

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Customer Rating: - Rubs on the 4100 series
Excellent idea, but it rubs on my new 4100 Bosch Saw, and is scratching it pretty good. Again, I like the idea, but it needs a lttle refinement for the fit on the actual table saw.

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Customer Rating: - Would be 5 stars if it actually fit my Bosch 4100 table saw :-(
Bought this for my new Bosch 4100 table saw (new model released several weeks ago). Manual said that this TS1003 is compatible but after installing...or trying, found that it does *not* fit the 4100. Will be calling Bosch to see if they have a replacement part that has been redesigned to fit. Strange thing is that even the instruction sheet that shipped with the TS1003 said that it fits both 4000 and 4100 model saws.