Listing Update...This is not so much a listing update as it is a point of emphasis.  We noted on these older Shimano 600 freewheels there are a couple of notches at the center of the unit that resemble the old Suntour freewheels...for the purpose of uninstalling the freewheel.  We note this as somewhat surprising, as we've usually noted Shimano freewheels to require a freewheel tool with a proprietary spline pattern for uninstallation purposes (but that spline pattern design must have come at a later date relative to the production of this particular freewheel unit).  So having said the above, we tried to insert our two-notch (and Suntour branded) freewheel tool into the two notches visible at the center of this freewheel unit, but quickly realized the notches on our Suntour freewheel tool were a bit too wide...maybe by a 1-2 mm's...so very close to a proper fit, but not quite.  As a result, I am left to wonder if other two-notch freewheel tools (maybe the PARK model) are a bit narrower and will fit fine.  If this is not the case, then I suppose the only option is to modify one of these two-notch tools by grinding down one side of each notch, to narrow each notch enough so that it will fit this particular freewheel.  My apologies for the lengthy explanation, but I found this somewhat surprising and wanted to alert other folks to the possibility of additional work necessary to unistall one of these freewheels at a later date.  Finally (and as most folks already know), I don't consider installation to be an issue, because a finger tight threading of one of these freewheels will suffice...with normal pedal pressure applied during a ride finishing the job of properly cinching the unit down to a snug fit.

Original listing...
This offering is for a new-old-stock Shimano 600 6-speed UniGlide (UG) freewheel with a 14-16-19-23-28-34 cluster in a nice gray/silver finish. This is a true old stock Shimano freewheel with a production window from the early 80's to the mid 80's (made in Japan) and is easily one of the best quality Shimano branded freewheel we have available. As most folks are aware, the 600/Ultegra parts designation was among Shimano's higher end offerings during this era...just as it is today.

In terms of compatibility, this is a freewheel, so it will only install on a threaded rear hub (as opposed to the newer cassette/splined freehub designs that are more common today). The threading is British/English, so it's 1.370" x 24 tpi (threads per inch), which was one of the more prominent standards during this period...and very near a couple of other standards. More specifically, there is the Italian standard of 1.378" x 24 tpi with a slightly larger thread diameter and different thread angle, but the same thread pitch as the British/English standard. Then there is the newer ISO standard of 1.375" x 24 tpi (which is the preferred specification of most newer freewheel manufactures) with the same thread pitch and angle as the British/English standard and a thread diameter between the British/English and Italian models. 

When considering the three aforementioned standards, conventional wisdom indicates there is some interchangeability among them...with a few caveats. More specifically the thread pitches are the same, while the thread diameters and angles are close enough that it's possible to install a freewheel spec'd to one standard on a threaded rear hub spec'd to a different standard (among the three included in this discussion). Although, one of the caveats is to avoid switching back and forth between standards, as there is still enough of a diameter and/or angle difference to prematurely wear-out/damage rear hub threading if this (switching back and forth) practice is employed. In other words, it's best to identify a freewheel standard (among the three mentioned) and then consistently use freewheels spec'd to that standard to help preserve the threads on a particular aluminum alloy rear hub. Additionally, we have learned these mix-n-match combinations may not be recommended for stronger riders and tandem applications...where there is additional drivetrain stress...as this combination may also result in premature thread damage to an aluminum alloy rear hub.  I realize this latter commentary is somewhat subjective...and maybe somewhat conservative...but we feel like it's better to error on the downside of product function, so there are no disappointments concerning product performance down the road.

Lastly, the spacing between the sprockets on this freewheel is fairly consistent with Shimano's newer 6-speed index shifting compatible freewheels and cassettes. Please understand we are not saying all Shimano 6-speed model freewheels are identical in terms of their quality, etc., but the sprocket-to-sprocket spacing of Shimano 6-speed freewheels that pre-date the index shifting models is generally close enough (to the index shifting models) that such older freewheels will usually function when matched with a vintage Shimano index shifting drivetrain.  Having said all of this, please also keep in mind the extremely wide gear range on this particular unit, as this freewheel will require a rear derailleur with a long pulley cage to reach all of the sprockets (in either friction or indexing mode).

As for condition, this freewheel unit is new and unused...and shows no signs of wear on any of the teeth. Listing Update...We only have a few of these freewheel units left in stock.