1-20 Siemens Industry, Inc. SPEEDFAX™ 2011 Product Catalog 1 LOAD CENTERS & CIRCUIT BREAKERS Load Centers Load Center OEM Interiors   UL Recognized Components. The letters “CU” in any catalog number represent copper bus bars. Feed thru lugs provided. Convertible to main breaker using the MBK main breaker kits.
http://w3.usa.siemens.com/powerdistribution/us/en/speedfax-product-catalog/Documents/sf-11-sect-01-018-024.pdf
Utility main breakerStandby power main breaker Load Centers Manual Transfer Interlock Kits for Load Centers and Meter Combinations Convert load centers or meter combinations into standby power panels ES Series Load Centers can utilize interlock kits: 1, 2, 5, 6, 7. Kits 3 and 4 can also be used on main breaker panels.
http://w3.usa.siemens.com/powerdistribution/us/en/speedfax-product-catalog/Documents/sf-11-sect-01-018-024.pdf
Convertible Load Center. A convertible load center does not have lugs or a main breaker. Once the owner decides which to use, a main lug or main breaker kit is installed by an electrician.
http://www.ehow.com/facts_5641637_breaker-panel-types.html
1 Standard 14-3/8 inches (365.1 mm) wide enclosures fit snugly between wall studs. 2  Tangential main knock-out eliminates the need for conduit offsets, which permits faster, easier installation. 3  BR load centers feature Robertson slotted square combo screwheads, which means only one screwdriver is need for installation.
http://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Residential/LoadcentersandCircuitBreakers/BRLoadcenters/index.htm
Rated 3.7 out of 5 by 3 reviewers. Rated 5.0 out of 5.0 by Sharok An excellent box for adding dedicated circuits I added eight dedicated circuits to my audio/video room using this box. It is small, easy to install and use. I also painted it since we get too much sun in Arizona. October 8, 2014. Rated 5.0 out of 5.0 by TheWiz Excellent non-metallic box I have installed over a dozen of these. For a lot of outdoor applications, I love these boxes, although they used to be half the price they are now.
http://www.homedepot.com/p/GE-PowerMark-Gold-125-Amp-4-Space-8-Circuit-Outdoor-Main-Lug-Circuit-Breaker-Panel-TPL412RP/202046212
Will not accommodate circuit breaker with shunt trip. 100 amp maximum breaker. Suitable for use as service entrance equipment when a main breaker (125A maximum) is back-fed in a branch position and used with main breaker retainer clip (Cat.
http://w3.usa.siemens.com/powerdistribution/us/en/speedfax-product-catalog/Documents/sf-11-sect-01-018-024.pdf
Eaton / Cutler Hammer BR3040L200G Main Lug Load Center; 200 Amp, 120/240 Volt AC, 1 Phase, 30 Space, 40 Circuit, 3-Wire, Combination or NEMA 3R.
http://www.cesco.com/b2c/category/Power-Distribution/Load-Centers-Panel-Boards/Main-Lug/_/N-lkkb
BR Load Centers. Specially designed for easy installation, Eaton's BR 1-inch load centers house the branch circuit breakers and the wiring required to distribute power to individual circuits. They serve as main breaker for service entrances or as main lug when adding circuits to existing service. The main breaker protects the main entire panel and can be used as a service disconnect. The branch breakers protect the wires leading to individual electrical loads such as fixtures and outlets.
http://www.eaton.com/Eaton/ProductsServices/Electrical/ProductsandServices/Residential/LoadcentersandCircuitBreakers/BRLoadcenters/index.htm
Store SKU # 589675. The load center includes a sturdy tin-plated copper buss bar and a galvanized box for increased durability and reliability. The one-piece interior removes and re-installs easily. Outdoor NEMA 3R enclosure. This load center is UL listed and ANSI Certified.
http://www.homedepot.com/p/GE-PowerMark-Gold-125-Amp-4-Space-8-Circuit-Outdoor-Main-Lug-Circuit-Breaker-Panel-TPL412RP/202046212
Siemens Industry, Inc. SPEEDFAX™ 2011 Product Catalog 1-19 1 LOAD CENTERS & CIRCUIT BREAKERS Product Category RESI EQ ® Load Centers—Circuit Breaker Enclosures 1-Phase and 3-Phase, 240V AC Max.  Will not accommodate 2-pole GFCI or circuit breaker with shunt trip. CSA Listed.42,000A IR maximum.
http://w3.usa.siemens.com/powerdistribution/us/en/speedfax-product-catalog/Documents/sf-11-sect-01-018-024.pdf
what is main lug load center
Main lug load center is a breaker. The main lug load center is a breaker.