In Win 303C Build Guide & Review: Hardline RGB Madness

We went all out by custom water cooling the new Intel Core-i9 9900K paired with an Nvidia GeForce RTX 2080 Ti for our latest build guide featuring the In Win 303C case in white. Complete with two 360mm radiators, we filled out the 303C and pushed its cooling capacity to the limits by overclocking both the CPU and GPU. If that wasn’t enough, we utilized hardline PETG tubing in our most ambitious project yet. Without further ado, here is our Hardline RGB Madness build!

in win 303c build guide review

Case Overview

The In Win 303C is very similar in design to the 101C and 301, sharing the steel body, plastic feet and minimal design. The design works very well and quality wise, the 303C is a great value for the money. The primary side panel is made of tempered glass and can be removed by releasing the latch at the top.

in win 303c

Upon removing the tempered glass side panel, we see the generous 360mm radiator mount at the top. There is also space on the bottom for an additional 360mm radiator. There are two 2.5” SSD/hard drive mounts on the motherboard tray. There are also several cable cutouts for cable routing. Additionally, there is space to mount a water cooling pump or reservoir using the back tray.

in win 303c review

The front is effectively minimal, we really like the look here. There is of course a power button, a reset button, two USB 3.0 ports, headphone and microphone jacks and a USB 3.1 Gen 2 Type-C port. The In Win logo is RGB based as are the front I/O ports, they all light up and look quite stunning in the dark.

in win 303c white

The back is relatively simple. Like the 101C and 301, the power supply is located up top however it is installed on its side in the 303C. The regular I/O area as well as the ventilated PCIe slot covers can be seen. There is a 120mm fan mount.

in win 303c white review

The secondary side panel is made of steel and has the attractive honeycomb pattern In Win has implemented on several of their cases. The side panel is secured via two thumbscrews at the top.

in win 303c white build

After removing the rear side panel, we can see the top section which has plenty of room for power supply cables, fan cables and fan/RGB lighting hubs. There are also two 3.5” hard drive mounts present on the backside of the motherboard tray for those still attached to their platter-based storage.

in win 303c build

Building the Beast

Before we begin, here is our parts list:

  • CPU: Intel Core i9-9900K
  • Motherboard: ASUS Maximus XI Hero (Wi-Fi)
  • Memory: 32GB Corsair Vengeance RGB Pro 3000 MHz DDR4 RAM
  • Graphics Card: ASUS RTX 2080 Ti Dual OC
  • Storage: Western Digital WD Black NVMe (2018) 1TB M.2 SSD
  • Storage: Western Digital WD Blue 2TB M.2 SATA SSD
  • Power Supply: Corsair RM1000x 1000W Gold
  • Fans: 6x Corsair LL120 RGB 120mm
  • Thermal Compound: Thermal Grizzly – Kryonaut 11.1 g Thermal Paste
  • RGB Lighting Strips: Corsair RGB LED Lighting PRO Expansion Kit
  • Custom Sleeved Cables: CableMod PRO ModMesh C-Series RMi & RMx Cable Kit (Black/Blue)
  • Fan Hub: SilverStone 8-Port PWM Fan Hub
  • Case: In Win 303C White

We began by installing our Intel Core i9-9900K into the ASUS Maximus XI Hero motherboard. Next, we added our M.2 based storage drives, a 1TB WD Black NVMe and a 2TB WD Blue.

asus maximus hero xi core i9 9900k

The last step before installing the motherboard in the 303C was to add the 32GB of Corsair Vengeance RGB Pro RAM.

asus maximus hero xi corsair vengeance rgb pro

Here is the Maximus XI Hero in the 303C, it fills the case out quite nicely with plenty of room left for the water cooling gear to come.

in win 303c asus rog maximus xi heroo

Water Block Installation

Here is our water cooling parts list:

  • 2x Alphacool NexXxoS ST30 Full Copper X-Flow 360mm
  • EK-Supremacy EVO RGB – Nickel
  • EK-Vector RTX 2080 Ti RGB – Nickel + Plexi
  • EK-Vector RTX Backplate – Black
  • EKWB EK-XRES 140 Revo D5 PWM High-Performance Water Cooling Pump w/205mL Reservoir
  • EK-AF X-Splitter 4F G1/4 – Black Nickel
  • EK-AF Ball Valve (10mm) G1/4 – Black Nickel
  • EK-CryoFuel Navy Blue Concentrate 100 mL
  • Thermaltake Pacific TF1 Temperature and Flow Indicator
  • Bitspower G1/4″ Matte Black Enhance Multi-Link For OD 16MM
  • Bitspower Matte Black Enhance 90-Degree Dual Multi-Link Adapter For OD 16MM
  • Bitspower Matte Black G1/4″ Male to Female Extender 90° Rotary Fitting
  • Bitspower None Chamfer PETG 16mm OD Tube Length 1000mm

Before going any further, we needed to prepare our ASUS RTX 2080 Ti Dual OC for water cooling by removing its heatsink. There are several screws on the backplate that must be removed prior to heatsink removal.

asus rtx 2080 ti dual oc heatsink removal

After removing the heatsink, we cleaned the existing thermal paste off. We added some new Thermal Grizzly Kryonaut thermal paste. Then we measured, cut and applied thermal pads to the VRM components: VRAM, drivers, MOSFETs and COILs.

asus rtx 2080 ti dual oc heatsink removed

Here is the EK-Vector RTX 2080 Ti RGB – Nickel + Plexi water block installed on the ASUS RTX 2080 Ti Dual OC. Very easy to install.

asus rtx 2080 ti dual oc ek vector rgb water block

In order to mount the CPU water block, we needed to align the rubber gasket and backplate.

in win 303c power supply area

Next, we covered our i9 9900K with the EK-Supremacy EVO RGB – Nickel water block. We also installed our RTX 2080 Ti with the EK Vector RGB water block.

in win 303c 9900k rtx 2080 ti build

Starting to run some cables to the CPU and GPU. Cable ties and velcro cable strips are very useful in maintaining tidy cable management in a case like the 303C where there are no dedicated cable management covers to hide wires.

in win 303c cable management

The CableMod ModMesh black/blue custom sleeved cables look fantastic in person! We also started to route the cable for the Thermaltake Pacific TF1 temperature/flow sensor.

in win 303c bottom radiator

We installed the EK-XRES 140 Revo D5 PWM pump/reservoir combo unit on the right side. Note, installation required the removal of the bottom 2.5” SSD mounting bracket.

in win 303c ek d5 water cooling pump

Next, we installed one of our Alphacool NexXxoS ST30 Full Copper X-Flow 360mm radiators on the top mount. Here it is, complete with three Corsair LL120 RGB fans.

in win 303c top radiator installation

Second Alphacool NexXxoS ST30 360mm installed with fans and our drain valve which pokes through the rear PCIe slot area. It’s starting to get crowded in here!

in win 303c alpha cool 360mm radiator corsair ll120 rgb

Tube Bending

Our first bend between the back port on the bottom radiator and the GPU block proved to be very difficult and required the use of a 90-degree fitting.

in win 303c 9900k rtx 2080 ti hardline water cooling

For our second bend, we tackled the CPU block to the temperature/flow indicator. We also connected the sensor to the top radiator.

in win 303c 9900k rtx 2080 ti bending petg tubing

Next, we added the tube between the pump/res combo and the bottom radiator. Simple and clean.

9900k rtx 2080 ti water cooling guide

Then we connected the CPU block to the pump/res combo. Another 90-degree fitting was used between these components.

in win 303c petg water cooling build

Lastly, we connected the top radiator to the GPU, again a 90-degreee fitting was used.

in win 303c 9900k rtx 2080 ti water cooled bitspower fittings

Filling the loop. We are adding liquid through the reservoir and turning the pump on and off to cycle fluid through the blocks and radiators.

filling hardline water cooling loop

All filled up.

water cooling loop filled

Complete Build Gallery

RGB Gallery

Battlestation Gallery


This monster computer was incredibly fun to build, whenever you are working with top-tier components it’s exciting and to custom water cool the best CPU/GPU combo is just icing on the cake! As you will soon see when we update our RTX/GTX benchmarking guide, the RTX 2080 Ti is a beast of a card and when paired and water cooled with the new i9-9900K, it makes for a very powerful combination. We believe we pushed the 303C to its limits as far as cooling is concerned. Yes, a 120mm radiator could probably be squeezed on the back but the tubing runs would have been extremely tight.

The double 360mm radiator combo works very well here with these components. Idle temps for the GPU are 29° C, with loads temps hovering around 42° C. With a 2,150 MHz core clock and 7,750 MHz memory overclock, load temps slightly increase to 46° C.

As usual, we’d like to thank all our partners for making build possible! We had no issues whatsoever with the components used in this build and recommend them all. We will be reviewing the individual components in the weeks ahead.

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Water Cooling Parts (Purchase on Amazon)

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