Original Bosch collet / union nut — part 2603312006. Machined metal collet nut with hex flats SW = 17 mm and an outer diameter of about 18.5 mm, made to clamp the collet and hold bits/attachments securely on compatible Bosch routers and straight grinders.

Fits a number of Bosch tool models (cross reference with the 10 digit product code to confirm fit):

- Bosch POF 400 / POF 400 A plunge router

- Bosch POF 500 / POF 500 A / POF 500 EA and POF 600 ACE routers.

- Bosch straight grinders GGS 27, GGS 27 C and GGS 27 L

- Bosch GKF 600 (GKF 600 CE trimmer) and several small die/grinder models (e.g., Bosch 1210 series) that use the 17 mm collet nut.

This is the original Bosch part 2603312006, intended as a direct replacement to restore safe clamping and runout performance — use where the factory collet nut is worn, rounded, or damaged.

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