The indoor PIR sensor is not as robust as the Outdoor PIR, but if if you know that you only need it indoor, why buy an outdoor PIR which is more expensive

• Monitored Range 88-degrees / 12m ‘long’ x 12m ‘wide’
• Adjustable Mount – rotate and pivot ball-n-socket type
• Indoor enclosure - Not weather proof
• Battery Operated sensor & transmitter, 2xAAA batteries included
• Method of Detection Pyroelectric Infrared Detector (Heat)
• Default: Fan Beam approx 78 degrees & 12m x 15m
• Options: Vertical Beam or Horizontal Beam adjustments
• RF Frequency transmitted 433.92 Mhz
• Output Power FCC part 15 approved, SAIDSA approved
• Transmission range up to 300m open space & 100m through walls
• Transmitter modulation OOK (On Off Keying)
• Code Programming User Programmable 256 codes
• Power Management - Battery saver settings
• Dimensions 110mm (long) x 60mm (wide)  x 85mm (incl. bracket)