Products & Equipment  /  Prep/Master Jr.
Substrate Technology, Inc.

Prep/Master Jr.

Prep/Master Jr.

The Prep/Master Jr. (formerly known as the Eco/Prep II) grinder from STI is ideal for polishing projects over 1,000 SF (93 m2). The new and improved design gives increased performance. Heavier head pressure allows a better grind and polish than the old Eco/Prep 500. Features include: an 8-gallon (30 liters) water tank; magnetic LED Light to illuminate front of machine or behind machine on the cutting path; screw-in carrying poles for easy two to three person lifting; and an on-board USB charger & phone carrier. The Prep/Master Jr. is easy to disassemble into two sections for quick transportation in the back of an SUV or pickup.

Features and Benefits


Motor 7.5 HP, Variable Speed Drive (5.6kW)

Power Source 220-240V Single Phase, 40A

RPM 250-500

RPM Variable

Tools Needed 6

Tools Attachment Style EG Proprietary Attachment System

Vacuum Hose Connection 2” (50 mm) — sold separately

Recommended Vacuum 3003G (300CFM) or equivalent

Production Rates: Mastic Removal 200SF / 19 M2 per hour

Thin Set Removal 200 SF / 19 M2 per hour

Mil Coatings Removal 50SF / 5 M2 per hour

Concrete Polishing 300SF / 28 M2 per hour

STI Diamond Systems that can be used on the Eco/Prep II:

Polished Concrete: EGT Polishing System (dry) & CLC Polishing System (wet-dry)

Polished Terrazzo: TPS Polishing System


50” L x 23” W x 48” H (127cm x 58cm x 122cm)

Working Width 23in. (58 cm)


7.5 HP, Variable Speed Drive (5.6kW) / 7.5 HP