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With Pre-Order, you can purchase the latest items added to our store in advance of them arriving with us.
Your Pre-Order is prioritized (at no additional charge); meaning that as soon as the product arrives with us, we can wrap it straight back up; ready for collection via Click & Collect or dispatch to you — it often never even hits the stock room shelves!
With Prelaunch, the date when we expect to receive the product ourselves is still a little too hazy to be confident in accepting Preorders.
So, instead, you can submit your email address for the item you are interested in, and we will email you as soon as stock arrives in the system.
Estimated Delivery & Collection Dates are given on Pre-Order and Pre-Launch products. They are for indicative purposes only and can change at any time without notice.
The dates we provide are based on information given by our suppliers. Whenever we get updated information from our suppliers we will endeavor to update the Estimated Delivery & Collection Dates provided on product pages.
Hassle free returns
If there’s a problem with something you purchased from us, you can either bring it to our store or ship it back. Ship returns via Ground UPS or insured US Mail (we do not accept CODs). We will refund shipping costs on damaged or incorrect merchandise. Merchandise returned that appears used will be subject to a restocking fee. (Labor fees are not refundable, i.e., custom built wheels.)Special Order items and bicycle are not refundable, in certain cases a return may be accepted with a re-stocking fee.
Returns over $100 must have a return authorization number clearly marked on the outside of the package or the item will be refused. A return authorization number can be obtained by phone or e-mail.
Season:Core
Brand:Shimano
Code:CY8903
The EW-JC304 is the junction box that makes 12-speed Di2 configurations work. It provides four SD300 ports arranged in a compact inline housing designed to sit inside your frame's downtube or bottom bracket area.
Most 12-speed Di2 installations use a simple three-wire setup: one SD300 wire runs from each shifter lever down to a junction inside the frame, then a single wire continues from that junction to the seatpost battery. The four ports give you flexibility in how you route your system. In the common three-wire setup, both shifter wires plug into one end while the battery wire plugs into the other end, leaving one port empty. That empty port needs a dummy plug, which Shimano includes with the junction box. All unused SD300 ports in the E-Tube system require dummy plugs to maintain proper sealing and electrical continuity.
The EW-JC304 can also be used to extend wire lengths by connecting two pairs of SD300 wires through the junction, essentially splicing four wires together while maintaining full power and data transfer. This is useful on larger frames or unusual routing situations where standard wire lengths fall short. The junction box is small enough to fit through most internal routing ports and tuck away cleanly inside the frame.
Installation requires the TL-EW300 plug tool. The SD300 connectors are smaller and more delicate than the older SD50 style, and trying to push them in by hand risks damaging the connection. The plug tool ensures clean insertion and removal without stressing the wires or ports. All Di2 components on the bicycle require the same firmware version. Using Di2 components with different firmware versions may cause malfunctions. Use the Di2 system checker to update component firmware.
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