Two BA15s type incandescent bulbs are used as spot lights in bullet fixtures for reading lamps and other such applications.

The base of a BA15s bulb is grounded and is a metallic 15mm diameter base with symmetric bayonet side-pins. A single contact at the bottom provides a contact for the positive lead.

The 1139 bulb dimensions are

     width 1.38 inches
     length 2.3 inches

The 1383 bulb uses the same base but measures

     width 1.5 inches
     length 2.6 inches

Both bulbs are frosted for better diffusion. Operating specifications for the spotlight BA15s bulbs are

	1139	1383
volts	12.8	13.0
amps	1.04	1.54
watts	13.3	20.0
candela (cp)	15	32
inital lumens	189	400
design lumens	75	160
lifetime (hrs)	700	300
replace with	RV3V	RV3V

The 1139 is less power and used in shorter bullet type fixtures. It offers the same luminosity as the low power 1003 bulb.

The 1383 uses the power level of the 1141, but with the inside reflector, provides a higher level of luminosity toward the front of the bulb. It is often found in longer bullet fixtures.

See donsbulbs.com for detailed specifications of the bulb you are replacing.