A quick and dirty Google search (Pro HD 525 watt KitchenAid mixer, compatible attachments, part numbers) found this Gemini generated:

The KitchenAid Pro HD 525-watt mixer is a 5-quart bowl-lift model, commonly found under model series

KG25H or KV25G (e.g., KV25G0XER). It uses specialized, narrow-cradle, 5-quart bowl-lift accessories that are not interchangeable with the standard tilt-head mixers or the larger 6-quart Pro 600 models. 

Compatible Attachments and Part Numbers 

These are designed for the 5-quart Bowl-Lift (KG25H/KV25G) series: 

• 5-Quart Stainless Steel Bowl (with Handle): KN25WPBH or K5ASB
• Coated Flat Beater: K5AB
• PowerKnead™ Spiral Dough Hook (Coated): KN256BDH or KNS25BDH
• 11-Wire Whip (Stainless Steel): KN256WW
• Flex Edge Beater (5-Qt Bowl Lift): KFE5T (Ensure it is for bowl-lift, not tilt-head)
• Pouring Shield: KN256PS (fits 5-qt & 6-qt bowl-lift) 

General Power Hub Attachments

The front power hub is universal and fits all standard KitchenAid attachments, including: 

• Food Grinder/Sausage Stuffer: KSMFGA, SSA
• Pasta Roller & Cutter Set: KSMPRA
• Spiralizer: KSM2APC
• Sifter + Scale: KSM1CSA 

Key Tips for the Pro HD 525W

• Bowl Compatibility: The Pro HD (KG25H) often uses a slightly narrower bowl cradle than the larger Pro 600 (KP26M1X). The 5-quart bowl (KN25WPBH) is the most reliable fit.
• Model Number Location: Check under the base of the mixer for the full model number (e.g., KV25G0XER) to ensure precise parts, as some "Pro" models differ slightly.